Many of the greatest guitarists aren't known for their technical abilities, their stage presence or revolutionising the way the guitar is played.
They're known for the one thing every musician (Beethoven excluded) NEEDS, no matter what instrument they play - their ears.
Good ears mean you'll be able to hear the right notes to play, feel the best rhythm and feel for the song and learn almost everything about the guitar faster.
Developing your aural skills, however, takes time. The good news is, even if you're a beginner guitarist, you've already had plenty of experience listening to music, so now it's really just a matter of practicing some active listening to help you hear the important parts.
Here's 3 things to listen out for to start developing your ears, eventually to the point where you'll be able to play songs on the guitar just by hearing them.
#1 The guitar part of a song
In a busy song, it can be very tough to hear what the actual guitar part is, just because so many musical elements combine to make a song.
To start, focus on acoustic guitar songs, where it's only a couple of instruments at most.
Listen to the guitar, keep your focus on it to hear where it goes and what it's doing from start to finish. Remember, you don't need to actually play the guitar part, just listen for it.
The next stage is to listen to songs with more than one guitar at a time, and try to focus on just one of them. This can be more of a challenge, but is very useful when you're trying to learn songs by ear or play duets!
Once you can do this ok, move up to electric guitar songs, full band songs, or anything you love listening to that has a guitar in it.
Remember, you don't need to understand HOW the guitarist is playing it, just WHAT it sounds like.
#2 The difference in tonality between chords
To begin, try playing Major, Minor and Power Chords. Even better, record yourself playing a bunch of these chords, throw the recordings into a playlist and set it to shuffle and try to identify which one is being played.
The actual chord doesn't matter, all we want to identify is the tonality. By that, I mean don't worry if it's an A or an Am, just try to work out if it's a major chord or a minor chord.
Once you can here those ok, start introducing other chords: Dominant 7th chords, Major 7th, Sus2 chords, Diminished chords or whatever types of chords you know how to play.
From here you'll be able to listen to a song and work out what type of chord to play, which makes it heaps easier to work out the actual chord they've played (especially if you know your chord theory).
#3 Melodies and basslines
If you're listening to a rock song like Smoke on the Water or Sweet Child of Mine, the guitar melody will jump out at you right away.
These songs are great to try and work out on one string, as it'll help you get used to the intervals between notes on the guitar (in other words, how far apart different sounding notes are on the fretboard).
Try a few easy rock riffs first, then jump into other songs with full chords and try to work out the bassline. Do it with your guitar in hand - after all, it's heaps easier to hear it when you can play it back!
The best part is, if you work out that the bassline is C - Bb - Ab- G, and you can hear that the chords are minor, dominant 7, dominant 7 and dominant 7, you can combine this knowledge to work out that the chords are likely Cm - Bb7 - Ab7 - G7.
The key to training your ears is to break everything down into small parts to listen out for. Don't try and work out the entire song, work out the first chord they play. Work out that first two notes in that riff.
Once you've trained yourself to hear all of these differences, you'll find you'll magically start learning songs faster, make less mistakes and will likely find it easier to write you own songs!