great WebMD slideshow on bad exercises to do

Thanks for the link, Banks! I have a question for you though, I was under the impression that squats are supposed to be done with the hips dropping below parallel, not keeping the knees at the 90 angle. Are there two schools of thought on this and is one better than the other or is it just personal preference?

they were talking about seated leg presses, not squats. The main things to be aware of with squats are a straight spine (through the whole spine, I.E. the neck should be straight with the back) and you don't "roll" your butt, which means that when you reach the point at the bottom of the squat where your tail bone starts to "curl" (your lower back will start to form a slight hump) downward, then you've gone to far as now you're engaging your lower back and core muscles for primary movers, that's bad as those muscles weren't designed for high load, they are stabilizers only (it's why people develop lower back problems when lifting things badly).

Basically with a squat, your shoulders should go straight up and down, your eyes should focus on a spot about a foot above your head on the wall in front of you and stay focused (this will keep your neck straight), you should perform the squat as if you're trying to sit in a small chair, the weight should be on your heels and the minute your butt curls you should stop, make a note of your knee angle, and not go that far the next time (do this with light or no weight, sideways to a mirror). As your gluts and quads (and hamis, and calves) get stronger, you'll be able to go lower, but that doesn't happen immediately.