There are plenty of tools out there to help you get the most out of your practice routine. Metronomes, backing tracks, hand exercisers, illuminated fretboards. Scale pattern stickers, books, DVDs ... You get the idea.
But there's one particularly useful practice tool that will dramatically increase your shredding skills while simultaneously helping you to nail those all-important rock star shapes when you hit the stage. And the surprising thing is, you already have it.
What is it?
We've all rocked out in front of a mirror with a guitar. Hell, most of us probably started playing in the first place after jamming out on a tennis racket in the mirror to Kiss or Metallica and thinking "this is actually pretty cool..." But aside from helping you to zero in on that perfect James Hetfield slow-slung slouch, a mirror can help you to perfect your technique, and probably even help to prevent serious problems like carpal tunnel syndrome and visible butt-crack.
There are several areas where a mirror can come in handy (aside from working on the aforementioned stage poses). The first is playing posture. I've taught so many students who started out with bad playing posture that needed to be corrected - they always seem to orient the guitar so that the neck is parallel with the floor, but this contorts their fretting hand into a weird position that makes it hard to change chord shapes, and especially hard to nail that dreaded open-position F Major chord.
Here's how a mirror can help: With your guitar at your side or otherwise out of the way, hold up your fretting hand. Look at the angle created by your knuckles, then place the guitar neck into your hand parallel to that angle, rather than