One of the most life altering tricks you can learn on the guitar is how to transpose using a capo. No kidding.

Well, maybe it won't completely alter your life, but it will help you to play more songs with less chords. And that's pretty cool.

Theoretically, you can take 1 chord, and using a capo, play 12 different keys with that chord. All it takes is sliding that capo up one fret at a time, and with each fret, you are playing in a new key, even though you are playing the exact same chord shape. Of course, you're not going to ever play with the capo on the 12th fret (just grab a mandolin for Pete's sake), but hopefully you understand the point.

Good luck and enjoy!