I use a clean grip. It seems like I fall forward a bit on the heaviest reps. This was my last set, where the form issues tend to show up a bit more.
Some queues I focus on:
-push knees out
I'd appreciate any input, as this is probably a lift I'll be focusing on more than back squats in my training career. Some goofy limb length ratios (long femurs) make back squats a lower back dominant exercise more than anything. Also, front squats tend to work my hips more than quads, oddly enough.