I started SS about 4 months ago and though I've now changed to a LeanGains style RPT program I'm still using Rip's book/DVDs as the basis for form, etc.
I video all my lifts so I can check my form and am happy with all my lifts except the squat. My form has definitely suffered as I increased the weight so for the last couple of weeks I've been deloading and concentrating on doing the movement correctly. The main problem I think was that I was moving my knees too far forward. Anyway I think I managed to sort it today - I did lots of reps at low weights until I was happy with the form, then slowly increased the weight up to about 80% of my previous maximum. The video below is my last set of 3 which was the heaviest weight of the session. Yes, I know the third rep does not have much depth - my legs were really tired at this point! It is mainly the knees I am concerned about, but I'd like to hear any other tips anyone has too.
Thanks in advance.
Squat 5/10/12 - YouTube