From "Starting Strength", hope it helps !
Question - How do I properly perform a squat?
The basics:
1) Get under the bar with your chest high and your upper and lower back tight.
2) Ensure your position is balanced from left to right, grip the bar, ensuring your grip is balanced from left to right.
3) Grip the bar as close to your head as possible. This will test your shoulder, elbow and wrist joint flexibility. The closer your hands are (within reason, your hands shouldn't touch your ears), the tighter your upper back will be, and the better the bar will sit on your back. Use a thumbless grip. You aren’t supporting the bar with your hands. You’re holding the bar DOWN against your back. Your wrist should NOT bend in either direction. It should be a straight line from your forearm across the wrist onto your hand.
4) Place the bar on your back across the low portion of the traps and rear delts (low bar position). Elevate your elbows as high behind you as possible, while keeping your chest upright. If your pectorals are sore, you will feel this as a deep stretch in the pectorals and possibly delts.
5) Inhale as deeply as possible, ensure your back is tight, bend down a bit and squat the bar out of the rack. Do NOT LEAN FORWARD and perform a good morning to get the bar out of the rack. You will lose tightness this way and, as a novice, expose yourself to injury.
6) Stand fully upright with the bar across your lower traps and rear delts, and clear the bar from the rack in 3 steps:
** Take 1 step backward with one foot to clear the rack
** Take 1 step backward with the other (trail) foot so that your feet are even
** Take 1 step sideways with the trail foot so that you get your heels to proper stance width.
Do NOT perform a "backward walk" with the bar. No more than 3 steps are necessary, total. Fidgeting with a few hundred pounds on your shoulders gets tiring. Squats are difficult enough as it is, no need to tire yourself needlessly prior to exercise execution with needless steps.
7) Make necessary adjustments so that stance width is proper, i.e. heels at ~ shoulder width, feet pointed in a "neutral" manner, ~30° outward. ~30° is "neutral" because as you widen your stance, your toes need to point outward in order to maintain proper patellar alignment with the thigh bones. When your heels are at approximately shoulder width, your toes will need to be pointed ~30° outward.
8) Keep your chest high and the bar balanced above the midfoot, take a deep breath, hold it, and squat down all the way. Do not look up, do not look down, do not look side to side. Keep your eyes focused on a point that is ~ 6-10' ahead of you on the floor, or if you have a wall close enough, focus on a point a few feet above the floor along the wall.
9) 4 basics of execution:
** Sit back (stick your butt out!)
** Squat down (bending/flexing the knees)
** Balance the weight by keeping your chest and shoulders upright while your upper body leans forward slightly to keep the bar above the midfoot
** "Keep knees tight" - i.e. don't relax your quads and simply "drop" into the bottom position, keep your thigh muscles tight throughout the motion
10) Once you have squatted down all the way into "the hole", without pausing or bouncing (more on this later), stand back up.
11) As you raise out of "the hole", you will be doing 3 basic things almost simultaneously:
** You will be pushing your butt upward
** You will be pushing your shoulders upward
** You will be extending your knees
** You will be forcefully contracting your upper and lower back muscles isometrically to maintain tightness in your torso
Do not begin to exhale (blow out) until you are near to completion of the repetition. This will cause you to lose tightness.
