Category Archives: Guitar Lessons

Don’t Beat Yourself Up Over It

One thing that I always say to a new student is “whatever new thing I show you when we get together… you’re not suppose to get it the first day.”  I think learning any instrument (or anything at all) requires time.   There are probably only a few people in the world who can pick up an instrument and just play it.  If you’re one of them, then pin a rose on your nose.  😛

If you’re new to an instrument, whether it’s the guitar or something else, don’t beat yourself up because it doesn’t seem like you’re getting it quick enough.  We all learn in our own way and at our own rate.  Don’t get discouraged because it’s not sounding the way you expect it to the first day.. or the second day.. or even after a week.  And don’t give up.  Sometimes, you might know in your mind how it should sound or what you’d like it to sound like but it takes your fingers/hands/body some time to catch up.

When it comes to technique, I don’t believe there’s “right” or wrong” or “good” or “bad”.  Although, there is “clean” and “sloppy”.  (But then again, maybe sloppy is what you’re going for.)  In any case, the point is that everyone’s fingers work differently.  What’s important is if the technique is serving you.  Does it produce the sound you want?  Does it allow you to play at the speed you want?  Does it create the feel you want?  And, probably most important, does it hurt?

On the other hand, analyzing the details and figuring out what exactly is keeping you from being able to play a certain part or lick is a great practice to have.  I think every great musician has to do this one time or another.  And once you find that little piece that’s giving you a hard time, just practice that short passage until you get it and then add it to the rest.  Or maybe there are a few parts that are difficult.  Practice them individually then string them together.

But if you don’t have that kind of time or just don’t want to spend the time, maybe the situation you’re in doesn’t really require you to play something exactly the way you’re thinking.  For guitarists, maybe it doesn’t have to be that particular position or that particular lick.  Sometimes it might be (more) appropriate to ask the question “this person played it this way to make this particular expression, how would I play this to express the same thing or something similar?”

But whatever you do, don’t beat yourself up over it.  It’s not worth it.

Guitar Lesson – Music Theory Part 8 – Scales and Modes

In one of the previous post, we looked at how you can use the major scale to create other scales by starting on a different note.  These other scales are also known as modes.  In that post, we started the pattern from the 6-note and created the minor scale:
          6  7  1  2  3  4  5  6  7  8
C major:        C  D  E  F  G  A  B  C
A minor:  A  B  C  D  E  F  G  A             
Now let’s take a look at what happens if we tried starting the pattern from the other notes.  Each scale or mode also has (Greek) name.  Remember, the root of each of the scales below is the 1st note.
C Ionian (major) :   C  D  E  F  G  A  B  C
D Dorian         :      D  E  F  G  A  B  C  D 
E Phrygian       :         E  F  G  A  B  C  D  E
F Lydian         :            F  G  A  B  C  D  E  F
G Mixolydian     :               G  A  B  C  D  E  F  G
A Aeolian (minor):                  A  B  C  D  E  F  G  A 
B Locrian        :                     B  C  D  E  F  A  B 
This gives us the basic idea of how to figure out the patterns of the other scales.  Let’s look at the different patterns side by side: (W= whole step, H = half step)

Ionian (major) :      W  W  H  W  W  W  H

Dorian         :      W  H  W  W  W  H  W
Phrygian       :      H  W  W  W  H  W
Lydian         :      W  W  W  H  H
Mixolydian     :      W  W  H  W
Aeolian (minor):      W  H  W
Locrian        :     

Now if we apply these patterns to the same root we can see the differences between the modes (which is really the important thing to remember):

                     1  2  3  4  5  6  7  8
C Ionian (major) :   C  D  E  F  G  A  B  C

C Dorian         :   C  D  Eb F  G  A  Bb C
C Phrygian       :   Db Eb F  G  Ab Bb C
C Lydian         :   C  D  F# G  A  C
C Mixolydian     :   C  D  F  G  A  Bb C
C Aeolian (minor):   C  D  Eb F  G  Ab Bb C
C Locrian        :   Db Eb Gb Ab Bb C

In some upcoming posts, we’ll start looking at what scale patterns might look like on the fretboard of the guitar. 

Guitar Lesson – Music Theory Part 7 – "out of key" chords

In Part 5, we looked at building triads from the major scale.  This resulted in: (just looking at 2, 3, 4, 5 and 6)

   ii   iii   IV   V   vi

Now, let’s turn them up-side-down and see what their major/minor counterparts might sound like.

   II   III   iv   v   VI 

Let’s try using the key of G.  So the “normal” chords would have been:

   Am   Bm    C    D   Em

So instead of these, let’s try: 
   A    B     Cm   Dm  E

Here’s a progression that tries to use all of them.  First, we’ll use all the “normal” chords.  Then we’ll play another sequence that will use some of the “abnormal” ones.  Here, some 7th chords will be used.  But the major and minor 3rds will still be “flipped”. 

|G    |D    |Em   |Bm   |
|C    |Am7  |D    |D7   | 
|G    |B7   |Em   |A7   | 
|C    |Cm   |G    |E7   |

|C    |Cm   |G    

Unfortunate, this example doesn’t use the 5-minor.  But we’ll get to that in the next example… 

Another set of chords that are “out of key” are the diminished-6 and diminished-7 chords (aka “6-flat” and “7-flat”).  This is not the same as 6 dim or 7 dim.  But rather, take the 6-note and 7-note of the scale and make them flat.   For instance:

E major scale:    E  F#  G#  A  B  C#  D#  E

So instead of C# and D#, use C and D.  Particularly, use their major chords.  Try this progression: 

|E    |E    |Bm   |Bm   |   (here’s that 5-minor)
|E    |E    |Bm   |Bm   |
|E    |E    |C    |D    | 
|E    |E    |C    |D    |
I hope these examples gave you some idea on how to “break out” of the scale and find other interesting sounding chords.

As you play with these chords more, you’ll start to hear their distinctive sound and you’ll be able to identify them more quickly when you hear them in songs.  You may notice that certain genres tend to use a certain chord a lot.  For instance, the 4-minor (as a “turnaround”) in 50s and 60s pop/rock, the 6-flat in (early) grunch, or the 2-major in (what I call “old school”) country.

Guitar Lesson – Music Theory Part 6.7.2 – diminished

This is part 6.7.2 which is a continuation on the discussion on “7”. The reason why this is in a separate post is because, quite frankly, I forgot.  And this is also a continuation on triads where we talked about how the diminished chord is what you’d get if you built the triad starting with the 7-note on the scale.

In this case, we’re looking at the 2 diminished chords: Half-Diminished and Diminished. 

Half-Diminished = 1 b3 b5 b7 
Diminshed       = 1 b3 b5 bb7 (the 7 is flat twice thus making it a 6) 

This might be confusing at first.  But once you “do the math”, you’ll see quickly that there isn’t much to remember.  Also, (in my experience) these chords are not very common (and for that reason, I’m not too familiar with them  :-).  But I love using them because they add such wonderful, (usually) unexpected texture.  Hopefully the progressions below will give you a flavor.

In my search for other material on these chords on the web, it seems like “diminished” is often also referred to as “diminished 7” (“dim7”).  But I was not able to find a slick way of pointing to the half-diminished chord except for “min7 b5”.

For the purpose of this post, I’ll be using “dim7” and “min7 b5”.

First, let’s look at the shapes.  Here are 2 ways of holding each.  For each of these, make a note of where the root note is (hint: either the A or D-string).

As mentioned above, the diminished 7th chord starts at the root and has a minor 3rd, a flat 5th, and a flat-flat 7th.  Interestingly, this puts each note in a perfect repeatable pattern.   For instance: 
Eb (major) = Eb(1) G (3)  Bb(5) 

Eb dim7    = Eb(1) Gb(b3) A (b5) C (bb7) 

What if we started with Gb?

Gb (major) = Gb(1) Bb(3)  Db(5) 
Gb dim7    = Gb(1) A (b3) C (b5) Eb(bb7) 

Notice that Gb dim7 has the same notes as Eb dim7!  How about for A? 

A (major)  = A (1) C#(3)  E (5) 
A dim7     = A (1) C (b3) Eb(b5) Gb(bb7)

You can image that you’ll get the same notes again if you start the pattern using C.

Since there are only 12 notes (C C# D D# E F G G# A A# B) and this chord uses 4, there can only be 3 different diminished 7th chords!

Now, let’s try using these in progressions along with other chords that we’ve already looked at in past posts.

Diminished 7th Example 1 
|C     |D     |Bm      |Em     |  (repeat) 

|C     |D     |Eb dim7 |Em     |  (repeat) 
This  progression is in the key of G which would have a Bm as the 3-chord.  (see previous post)
For hearing the full effect of the dim7 chord, try playing the 1st line (maybe repeat a few times) then try the 2nd line (and repeat a few times).  You’ll notice that the Eb dim7 replaces the Bm.  And you might hear how the Eb dim7 provides more “energy” and “tension” to be “resolved” by the Em chord.
Diminished 7th Example 2
|Dm7     |G7     |Cmaj7      |Db dim7  |  (repeat) 

This example in the key of C is a more jazzy example (or funky a la Sunday Morning by Maroon 5??).  Again, the dim7 chord provides a tension to be resolved by the following chord (Dm7 in this case).  And you can hear a moving bass line from: C > Db > D. 
Half-Diminished Example
|Bm b5   |E7     |Am       |Fmaj7     |  (repeat) 

This example might be a bit more classical or Spanish (in fact, try strumming Flamingo style… perhaps more on this later).  This would be considered to be in the key of C.  The Bm b5 chord is the “natural” chord create from the 7-note in the scale.  While the E7 is “out of scale” (E is the 3rd note so it would have been Em using the notes from the C major scale).  The Bm b5 chord “wants to go to” the E7 which “wants to go to” Am.
Hopefully you now have an idea of how diminished chords can be used to create tension and unrest and that you found these examples useful! 

Guitar Lesson – Music Theory Part 6.7 – soft, jazzy, and bluesy

All 7 and we’ll watch them fall…

In a previous post, we talked about major and minor scales and how they share some notes while other notes are different.  7 is one of the ones that are different.  So when adding 7 onto a triad, you can either add the major 7 (“maj7”) or the minor 7 (just “7”).

You can add the 7 onto a major or minor chord.  So using the root note of A, we can have the following chords:
A7       – A C# E G
Amaj7    – A C# E G#
Am7      – A C  E G

I have not personally heard of the major 7 added to the minor chord (Am maj7??).

The changes between these chords are small but their uses and sound are very different.  Below, I’ll try to give a few examples of how you might them being used…

7 Chord
The 7 chord tends to feel unresolved.  This is a very common chord in blues.  For instance, in this common blues progression, you can substitute all the chords with the corresponding 7 chord:

|A    |D    |A    |A   |
|D    |D    |A    |A   |
|E    |D    |A    |E   |

So using 7’s, this would be:

|A7   |D7   |A7   |A7   |
|D7   |D7   |A7   |A7   |
|E7   |D7   |A7   |E7   |

Or using the number system:

|I7   |IV7  |I7   |I7   |
|IV7  |IV7  |I7   |I7   |
|V7   |IV7  |I7   |V7   |

Often the 7 chord is used to “propel” the music toward its relative 4th.  For instance, A7 (I) will want to be followed by D (IV).  Here’s an example:

|A    |A7   |D    |Dm   |   

But you can also look at the relationship backwards which is D (I) and A7 (V7).  Here’s an example:

|D    |A    |A7   |D    |

These are fairly common in folk, hymns, and rock.  Here’s a some-what folk-y example: 

|D    |A    |A7   |D D7 |
|G    |A    |D    |D7   | 
|G    |E7   |A    |A7   |  (back to top)

In this example, the A7 (V7) on the 1st line is used to lead us back to the D (I).  The D7 (I7) on the 1st line leads us to the G (IV) on the 2nd line.  The D7 is used again on the 2nd line to lead us to the G.  Then E7 (II7) is used to lead to the A (V) and the last A7 (V7) is used to lead us back to D (I).

Major 7 Chord
The major 7 chord tends to be softer sounding.  Often, this chord is used as a substitute for the IV chord in a progression.  For instance:

|C     |F    |  (repeat)
|C     |Fmaj7|  (repeat)

When we look at the notes that make up these chord it becomes more apparent why this “works”:

C      – C E G

Fmaj7  – F A C E

<— T = thumb

Another very popular variation on this is to use the maj7 chord for both:

|Cmaj7  |Fmaj7  |  (repeat)
Cmaj7  – C E G B
Fmaj7  – F A C E

In essence, we’ve give the F (IV) some characteristic of the C (I) by using the E (the 3-note) in both chords.  You can take this a step further by adding the 6-chord (vi).  In this case, this would be Am:

|C   |Fmaj7 |Am   |Fmaj7 |   (repeat)

Cmaj7  – C E G B
Fmaj7  – F A C E
Am     – A C E

Another way to look at this is that the E note (the 3-note) is used as a pedal note.

Minor 7 Chord
This is probably my favorite (definitely top 3). I love using this chord. Here, the 7 is the minor 7 relative to the root note. And it helps to soften the chord.

Am7     – A C E G

Recall that the minor 7 is a whole step from the root note. When this is used with the 2-chord (ii7), then the “7” is the same as the root note of the 1-chord (I). For example:

|Am7   |G     | (repeat)

Am7     – A C E G
G       – G B D

So what if we substituted the 6-chord with its 7 (vi7)?

G (I)      – G B D
Em7 (vi7)  – E G B D

<— standard shape

Now, let’s add this to another example we looked at before: (

|G    |Cadd9 |Em7  |Cadd9 | (repeat)

But instead of using the standard shape shown above.  Try this one instead:

Guitar Lesson – Music Theory Part 6.6

I’m not a big fan of 6.  I don’t know why… maybe under different circumstances we could have been friends… but sometimes a number just rubs you the wrong way… know what I mean??

I’m afraid I don’t have a lot of advice on how to use chords with 6 in them.

I think my favorite way of holding this chord is using this shape.  It sounds pretty nice when you use arpeggios.

I’ve been told that the 6 chord is use in a lot of Christmas music.

But one of my favorite chords with the 6 note in it is by adding it to the sus4 chord.

Sometimes I like to use this instead of the normal sus4 chord.  I like holding this using the 1st finger across to hold all 3 strings (in this case, on 2nd fret) then apply the 2nd and 3rd fingers in front.

Try going back and forth between this chord and the normal root chord (in this case, A major).

Another way to think of this chord might be D/A (that’s “D over A” or “D slash A”) or 2nd inversion D.  We’ll get into those type of chords in future posts.

Guitar Lesson – Music Theory Part 6.4 – 4 and more sus2

1, 2, 3, 4 … come on baby say you love me (

Alright, so we’re going to talk about the 4 note.  The most popular use of this note on guitar is probably the sus4.  Here are the common shapes for this chord:

In these chords, the (major) 3rd is not played and is “covered” by the 4th.  The 3rd is shown using the white dot.

Very similar to the 2 chord, the 3rd is not played so these chords are ambiguous.  They’re not major or minor.

A common (proper? classical?) way to use the “sus” chord is to use the suspended (that’s what “sus” stands for) note as a way to “smooth” out a transition between two chords.  For instance:
     G    Dsus4    D

The G is the “preparation”.  The Dsus4 is the “suspension”.  And the D is the “resolve”.

Here, the G is made up of: G-B-D.  Dsus4 is: D-G-A.  So the G is suspended.  (If you use the open-string shape for G and the Dsus4 shown here, the G on the high-E string is suspended.  If you use fingers 2, 3, and 4 to hold the G, then you’ll probably find that you don’t need to lift your pinky going from G to Dsus4).  And D is: D-F#-A.  So the 4th is resolved by the (major) 3rd.

In these diagrams, the 3rd is shown by the white dot which is “covered up” by the 4th.

Another common use of these chords in modern music is going between the sus chord and normal triad.  This happens a lot with both sus2 (see part 6.2) and sus4.

To hear some examples, check out:

Black or White (Michael Jackson) — the riff basically goes from sus4 to major then sus2 to major

Another way to use the 4 note, of course, is to leave the 3rd in.  In that case, we’d be adding the 4.

I find that this chord by itself could be a little strange sounding.  But it makes a lot of sense when you play it along with other chords.  For instance, try holding the open-string C chord the same way (ie include the G on the high-E, shift this shape up 2 frets).  Play the C then Dadd4.  C, of course, have the G in it also (and it’s been suspended on the G-string).

Another example of how this chord might be used is in the song Hysteria by Def Leppard (wow… I’m really showing my age with these examples!):

Watch Phil Collen’s hand position (that’s the guitarist on the left for you youngsters) .  In this case, I would consider that the riff is made out of the 1, 3, and 4 notes (D, F#, G) and it repeated as a “theme” over D, G and Em (actual progression is: ||D    |G    |Em  G |D   :|| )

Okay, yes, there was a lot of use of sus4 in the 80s!  Probably too much in fact!  (Although, I think these songs “technically” came out in the early 90s)

Let’s try this more recent example of sus2.  Here’s Bad Day by Fuel (well, relatively more recent):

Here, the beginning chords are:  A   Asus2   A

Again, the play is with the 3rd.

Sometimes, the sus4 chord might be used as a “substitution” for the V chord and the sus2 chord in place of the IV chord.  (see M&m post)  

There are a few ways guitarists like the play these.  Here is one example:

|G    |Cadd9   |Dsus4   |G      |

For this progression, try holding the G using all 4 fingers.  Your ring finger should be holding the B-string on the 3rd fret and your pinky on the high-E strin gon the 3rd fret.  These are now holding notes D and G.  (see G<–>Cadd9 Thing post)

Cadd9 also has these notes.  Then Dsus4 as well.

In this case, the 4 note is not used as a way to “mask” the 3rd (in the D chord), necessarily.  But the G is suspended throughout the progression.  This is also sometimes called the “pedal point” or “pedal tone”.

For a sus2 example, try:

    |E      |Bsus4     |Asus2    |E       |

Guitar Lesson – Music Theory Part 6.2 – 2 & 9

We’re continuing our look at the other numbers: 2, 4, 6, 7, 9.  I’m going to try to give you some ideas how you might use these chords.

This is part 6.2 because we’re going to look at the 2 chord.  😛

Disclaimer :- The following tips are purely based on my own experience, reading, and experimentation.  Results may vary.  Check with your ears to see if these chords are right for you.  Side effects may include: more time spent with your guitar, creative ways of holding chords, and creative voicing and dressing up your chords.

2 & 9

To be completely accurate, I guess most guitar chords using the 2 note is actually the 9.  What I mean by that is that most of the time, the 2 note being played in most of these chords are not actually 1 step away from the lowest root note but rather an octave + 1 step.  It’s very rare that you’d play a root note with the 2nd note on the next string.  For the most part, it’s just kind of hard to do.  🙂  And the notes tend to become “mushy”.  So I’m going to talk about the 2 and 9 together (interchangeably).

2 if fun.  I like the 2.  It’s very versatile… kind of like a plain white tee… you can where it out, where it under something, where it like pajamas.  Because the 2 chord doesn’t have the 3rd in it, it’s ambiguous — it’s neither major or minor.  So it can be used to “mask” the major or minor.  For instance, try this progression:

    Em   C   D   Asus9  (a la “Drive” by Incabus)

Now, try substituting the Asus9 with either A or Am.  You might find that the A sounds okay.  But the key should be G which should make it Am.  But if you try Am, you might find that it’s too dark and lack the “driving” (pun intended) characteristic of the song.

I also like using the 2 with the 3rd, both major and minor.  For instance, try this chord: (Emin9)

Notice that the root is E.  The F# is played on the D-string while the G is also played (on the G-string.  In this case, the 7 (D) is also played on the B-string.

Try some arpeggios (allow notes to ring but only play one at a time).

Here’s a fun progression.  Try playing Emin9 followed by the one on the right which I’m calling C-5+9.

And here’s another way to hold the min9 chord which also sounds great.

Another one that I really like is adding the 2 note with the major chord which might look something like this:

Notice in this version of Cadd9 (see previous post for other version), both the D and the E are played.  And in fact, the D and E are only 1 step apart.

I usually like using this chord to create a smooth/gentle end to a song.

This type of chord is fairly common on the piano in pop.

Well, there you have it.  A few different ways to use the 2 (or 9) notes… without 3rd, with minor 3rd, and with major 3rd.

Guitar Lesson – Music Theory Part 6 – the other numbers

Sometimes I think the other numbers must feel like what’s-her-face on the Brady Bunch (“Marsha, Marsha, Marsha”)… what’s her name…??  Doesn’t matter… Anyway…

In this lesson, we’re going to take about some of the other numbers that are not 1, 3 and 5.

Just to recap… We use 1, 3, and 5 to build triads.  When we do this, we find that we get major chords and minor chords.  The 1 and 5 are the same for both.  The major chord uses the major 3rd while the minor chord uses the minor 3rd.

So let’s look what we can do with 2, 4, 6, 7 and 9.
Often, people will use sus2 and sus4.  The “sus” is short for “suspended”.  In these chords, the 3rd is not played and is substituted by the 2 or 4.  For instance, Asus2 would be made out of: A B E.  While Asus4 would be played using: A D E.

The 6th chord is simply the normal triad with an added 6th.  For C, this would mean the notes are: C E G A.

The 7th chord is simply the normal triad with an added 7th.  Normally, if it just says “7” as in C7, the “7” refers to the minor 7th.  So C7 has: C E G Bb.  You can also add the 7th to the minor chord.  Cm7 would be: C Eb G Bb.  The major 7th can also be used but it’s normally written as “maj7“.  Cmaj7 would be: C E G B.  

The last number we’ll talk about for this lesson is the 9.  As you may recall, the 1 and 8 notes are the same note except the 8th is an octave above the 1.  The 9th is therefore the same note as the 2nd also an octave above.

For 9, there are 4 chords worth mentioning…

add9” (ie Cadd9, see previous lesson) — This is probably the most common one for guitarists.  For instance, Cadd9 would be: C E G D.

9” — This is not the same as “add9”.  In this case, the minor 7th is implied.  So the notes for C9 are: C E G Bb D.

maj9” — In this case, the major 7th is implied and so Cmaj9 would be: C E G B D.

min9” — Very similar to the “maj9”, here the minor 7th is implied and so Cmin9 would be: C Eb G Bb D.

There are also 11th and 13th chords but we’ll look at them another time.

In one of the next posts, we’ll look at how these chords might be used.

Guitar Lesson – Music Theory Part 5 – M&m


I know… very boring… but keep reading… once you get a hang of this stuff, you’ll see the fretboard in a whole new way.

In the last lesson, we talked about what a “major” chord is verses a “minor” chord.  And we also looked at building “triads” which are basically 3 notes played together.  Major and minor chords are triads.  And we also looked at how there are different shapes for the major and minor chords that you can place at different frets to get all the chords.

We used the C (Major) Scale to build a triad starting with C and we got the C (Major) chord.  But what if we built triads using the rest of the scale??  Let’s see…

  1  C — C E G = C
  2  D — D F A = Dm
  3  E — E G B = Em
  4  F — F A C = F
  5  G — G B D = G
  6  A — A C E = Am
  7  B — B D F = Bo (diminished)

Let’s look at a few of these and see why they might be major or minor.  Remember that a chord is “major” if its 2nd note is a “major 3rd” from the root (2 steps).  And the chord is “minor” if its 2nd note is a “minor 3rd” from the root (1 1/2 steps).

The 1st chord we get has the notes C, E, G.  The E is 2 steps away from the C so this is a major chord.

The 2nd chord we get has the notes D, F, A.  The F is 1 1/2 steps away from the D so this is a minor chord.

The 3rd chord we has the notes E G B.  E is 1 1/2 steps away from G so it’s minor.

The 4th (sometimes called the “sub dominant”) and 5th (sometimes called the “dominant”) chords are both major because their 2nd notes are 2 steps away from their root (ie F->A and G->B).

The 6th chord is minor.  This is also the “relative minor” to the 1st major.

The 7th chord is different.  Not only is the 2nd note a minor 3rd from the root (B->D).  But the 3rd note is not a 5th!  B’s 5th is F#, not F.  So the F is flat or “diminished” from the normal 5th.  Therefore, this chord is called the “diminished” (usually denoted by a superscript O).

Let’s review and use “M” for major and “m” for minor (and “o” for diminished).  We have:
  1  2   3   4   5  6   7   <– numberth note in scale
  C  D   E   F   G  A   B   <– notes for C scale
  M  m   m   M   M  m   o   <– [M]ajor, [m]inor, or diminshed
  I  ii  iii IV  V  vi  vii <– roman numerals (uppercase = major)
If you go through this exercise with all/any of the scales, you’ll find this pattern in every case.

Why is this useful?

This is also sometimes called the “Nashville System“.  Instead of writing out the specific chords, for instance: C, G, Am, F, the chart might read: I, V, vi, IV or maybe: 1, 5, 6m, 4.  The expectation is that you would be able to figure out which chord it is if/when provided the key (ie root or scale).

When you’re learning a song, if you don’t have an instrument handy (and you don’t have perfect pitch), it might be hard to figure out what notes/chords are being played.  But if you train your ear to hear “relative pitches” and use this basic understanding, you can learn a song by ear simply by identifying the chords by their numbers.  What you’ll find is that each chord has a distinct feel/flavor.  And no matter which key you’re playing in, each chord can serve the same function.  For instance, if you play a progression (a sequence of chords that repeat), you may find that the V chord likes to be followed by the I chord.  
I do most of my learning this way for covers.  I find that it gives me 2 advantages:
1) I can learn a song in the car while driving
2) I’m not “stuck” on a particular key in case we decide to play it in another key (usually requested by singers)

TIP 1 :- Listen to the bass notes.  Most of the time it’s easier to identify the chord using that note.
TIP 2 :- Pick a key.  Start with the I chord.  Then play another chord from the scale (ii, iii, IV, V, vi, or vii) then play the I chord again.  See if you can hear the differences and movement.

This might come in handy when trying to transpose on the spot.  For instance, let’s say you learned the song in C.  The progression is: C, Am, F, G.  Instead of think of the chords by their letters, think of them as: I, vi, IV, V in the key of C.  Now, let’s say you want to play this song in E.  And you might remember that the notes to E (major scale) are: E F# G# A B C# D# E.  So this progression in (the key of) E is: E, C#, A, B.

In fact, transposing on guitar is extremely easy (much easier than piano IMHO).  If you have learned your progression using barre chords, and you’ve been playing the above progression in C using 3rd fret (A-shape for C major), you can shift your entire playing down 4 frets to E (7th fret on A-string) and wa-la, you’re playing in the new key!

If you’re writing your own songs, this might give you some basic starting point for coming up with a progression.  This can serve as the basic guide or “rule of thumb” for what chords might sound good together.  This can also serve as the rules to break.

This also helps when improving (a solo that’s not predefined).  Usually in these situations, you already know what the progression will be.  By remember what notes are in the chords coming up, you can quickly figure out what notes might sound good over them (vs other notes that won’t sound so good… unless that’s what you’re going for).  This becomes even more powerful when you think of this in terms of numbers.  For instance, think of the V chord as having notes 2, 5, 7 from the scale.  For guitar, this means you just need to know the “starting point” (ie key, root, scale).  So you know that if you play one of those notes from the scale, it’ll harmonize with the chord.

Once you start analyzing songs this way, you’ll confirm what you’ve probably heard others have said, “this is basically the same song as ____”.

Over time as you develop your ear, you’ll hear the same patterns over and over again so learning new songs becomes very easy.  (ie *yawn*, another 1 5 6 4 pattern?!)