If you are want to improve some of you music knowledges, you are can try to play music by ear. Maybe, first time it's being hard - but with practice, you can play some parts and riffs in a few minuites.
You can start play by ear, almost in a few days, after you buy musical instrument, and the only thing you need to know - it's basics of music theory.
It's a lot easier, when you are know some basic intervals, and can faster found the right. Like example, if you learn Linkin Park - Crawling, now you are remember in your head, how Perfect Fifth is sounds, and can recognize it out of other 11 intervals. Or LadyTron - Evil is use Minor Sixth.
If you don't have one, you can download some software, that simulate piano, or some synthsizer, and try to found the right notes on keyboard. It's also very good method, that give you more experiance. Like first of all i play Linkin Park - Crawling on Piano, and then just write notes for guitar.
You first song should be something easy, so i can give my list of songs, i learn first, but you can find something in your collection:
It's have sense to try play this songs on one string. As example, first i learn Linkin Park - Numb on second string, and then just move notes to other strings, and it's sounds the same, as in original.
This is songs, that help me to learn this very important part of music theory. Don't worry, if you are have problems with some of them, i waste about half year, to learn all this songs, some of us can learn it faster or slower, just do this good, because life is long.