You're not engaging your post. chain as much as you could.
Remedy: Sit back more. Do box squats. Learn how to do good mornings/RDLs to get your glutes really involved. All this really depends on your goals though, and I don't know/care enough what you're training for(sorry).
Your tailbone is tucking towards the end.
Remedy: Stretch, mobility work, practice, practice, practice. Work an imbalances, tight hip flexor, glute activation etc.
It's not what I consider to be a full squat, definitely parallel tho, so that's good.
Remedy: Parallel is fine. Stance really depends on your goals. So no direct input.
You don't want to come out of your arch tho, both upper and lower back.
Remedy: Work on technique with lighter loads until you can stay tight the whole time.
Watch this series
More good tips here as well
http://www.dieselsc.com/how-to-squat/Videos from diesel
