"don't squat past parallel, its bad for your knees and overall its dangerous" is probably at the top of any list. In fact that reminds me, I was doin some goodmornings one time and this guy next to me thought in his retarded little mind that I was trying to squat and was just fuckin up the form, of course he had never heard of goodmornings in teh first place so he had no place to even open his lips. So he told me I should not squat like that, I proceeded to explain what I was doin, and I was warned to never place that much stress on my lower back, in fact I should never even train it directly cuz I might just break. "thats dangerous man, don't you know"... the guy was like 30 and looked like he never lifted a weight in his life. needless to say when we were finished he knew his role and shut his mouth.