Oh, one tip that I found pretty useful if, like me, you don't have a gym buddy. Grab your phone, prop it up against a wall or a bit of equipment, and video yourself from the side while you're lifting.

I'd had a couple of people tell me that my squat form was poor and that I was going to injure myself, but I found it impossible to figure out what was going wrong as I had no feedback loop. Once I could see myself on video, I could try different techniques and see how they affected my form. Starting Strength has a lot of writing on how to recognise and train good form, so once you can see yourself it's not too hard to correct.