What's up holmes? Well, first of all you're gunna need some heavy gage strings. If you tune to drop C with regular 9 gage it's gunna sound like crap no matter what you do. Second of all, you're probably going to blow out your amp because guitar amps aren't built to take such low frequencies. Big name bands like Sevendust, Korn, and Tantric that play in drop C have special "tricked out" amps that can take their kind of abuse. Just a few words of caution.

Ok, to tune to drop C you first need to tune your entire guitar down a whole step (i.e. the E string goes to D, A to G, D to C, etc). Then drop your low E string another whole step to C. That's it. Pretty easy huh? . . . you'll be sounding like Linkin Park in no time (if that's a good thing . . . lol).