Soldato
It looks like you sit down and run into an obstruction (hips) near the bottom of your squat, then have to move your body around that to get the rest of the way down. One of the more helpful things I found with working on my squat was taking the time to find a foot position where you can sit down between your legs smoothly (see that Tian Tao vid I posted on the last page) where everything seems to move in one go, rather than in stages. There's some good videos by Juggernaut Training Systems on that on YouTube.
The other thing is to find your balance so that the weight of the bar is centered over the middle of your foot, so that there's even pressure between your toes (big toe should feel like it's pressing into the ground somewhat) and your heels. This should not shift during the movement at all, the weight should not transfer forward or back. A way of maintaining this balance during your descent I found works for me, is to image someone behind you has tied a rope to your hips, and someone in front of you has tied a rope to your knees. The squat is then initiated when both people start pulling at the ropes, so the combination of knees forward and hips back results in your sitting more or less straight down but keeping the tension in the legs rather than what tends to happen for most people, which is a loss of tension in the legs, shifting the weight back into the heels and then using the back to heave the weight back up.
