Quote Originally Posted by dth4lf View Post
1)Make sure your feet are shoulder width or slightly wider apart.

2) Be sure to point your toes out a bit. Not quite a 45 degree angle, possibly around 30 degrees. This will ensure that when you squat your thighs will be out of the way of your torso as you lower into position.

There's obviously a bit more to it than this, but you should be able to squat damn near ATG by following these two ques.
There's no particular reason one needs to squat ATG to benefit from squats however. As one who used to do it as a matter of ego more than benefit per se in my younger days, I have come to appreciate the fact different people have different mechanics, flexibility, goals, etc and there's no absolutes in the need for ATG style squatting and benefits.