RE: m-audio fast track pro
Looking at the thing at GC, it has 2 XLR/1/4" combo inputs. You plug the guitar in, push the Inst/Line button to select Inst input. And since a guitar is usually mono, you may need to choose Left input in the MC track like Gamblerschoice wrote, unless the Fast Track is one of those devices that only sends a stereo signal.
Consult the M-Audio help file or manual for the best info, since I don't have a Fast Track. Or maybe someone here has one who can help.