Foot Pressure In The Squat
Many issues with the squat can be corrected by adjusting foot pressure during the movement.
On the descend: Break with the hips and the knees at the same time and keep you weight over the middle of your foot. Be careful not to sit back to lean forward too much at this point. Simply, keep your weight over the middle of your foot. This will help put you in a better position to drive out of at the bottom of the squat.
Once you hit the bottom of the squat, keep your whole foot on the ground while pushing out of the hole through your big toe area. This will help engage the quads which are at their best position to help the movement at this point. Also, keeping your knees over your toes as long as possible while going up will help with keeping the quads engaged and not letting your hips shoot up.