Every guitar player has some experience with playing by ear. Whether you tried to match the sound of a song, or you were able to correct a mistake in an online tab because it didn't sound correct, you were using your ears acutely for both. To start training your ear, listen to the broad categories of music theory—the roots of chords, types of scales, and types of chords.

The first thing to do is try to match a single note. It would really help if you could get a guitar-playing friend to help you with this, and then you could quiz each other. If you don't have a friend who plays guitar, don't worry. Almost anyone can muster up enough ability to play one note on the guitar—even someone who doesn't play. You could also ask your teacher to help you with this exercise.

To start with, have someone play a note on a certain string and tell you what string it's played on. (This isn't a guessing game—you won't be able to tell one note name from another unless you have perfect pitch, but you can tell how far apart the notes are.) When you start, see if you can tell if you are too high or too low. You're not going to know exactly how far away, but if you can narrow the direction you have to move, you're starting to hear more acutely.

Be patient and try to get as close as you can to the note. Your first few attempts may not yield much success, but like anything else you've studied, you need to practice to get good at it. Keep trying different notes and different strings. Some students hear better in certain ranges of the guitar, and that is normal.

As you keep doing these exercises, listen for the important factors of how high or low you are and how far you should move back. If you can get it down to two or three tries, you're doing very well.

Don't make the mistake of believing you have to start at the beginning of a song. You should start wherever you're comfortable starting. Start where you can succeed! Ear training is a slow process and can be quite frustrating. Just remember that being able to learn a new song is akin to learning how to play fast and clean—neither one happens without practice. Try to practice ear training each day when you play.