Annie spoke today about your grip in the back squat. This of course may not be your first thought when considering a leg and hip dominant movement, but what your grip is like and where the bar sits is very important in the back squat. She spoke about trying to grip the bar with your clean grip. A narrower grip like this will create a lot of tension between your upper body and the bar, syncing the bar in nicely to your rack position. Having this engaged grip will also give you the ability to drive out of the squat better. If your hands are wide and your rack is loose then the bar is just essentially sitting on your back without any tight connection to your upper body. The result is you will not be able to drive against it as efficiently. If the shoulders and grip allow it, having a narrower grip will keep the bar more controlled and with that tension allow you to move out of the squat more effectively.
Here is Shane and Helene squatting with their upper bodies engaged.
3 x 12 Back Squat
bench press (increasing weight each set)
10 one-arm dumbbell rows (each arm)