I have a mac and garageband. Currently i connect the guitar via the mic in but im told thats not the best method.

My guitar teacher uses a Line 6 floor pod x3 live, and connects to his computer via USB. I dont have the cash for one of these just yet, so im wondering, whats a cheap way of hooking guitar to a pc?
You could try and get an old Digidesign MBox (as in not version 2).
They say the old woman's got the wisdom
'Cause she couldn't read the clock anymore
She said "The numbers don't represent the moments"
Says she don't see what all the ticking's for