According to Strength Coach Jason Ferruggia, a perfect squat should look like this:

Grab the bar with an even grip, wider than shoulder width and be sure to squeeze it as hard as you can. You should be making white knuckled fists and the tension should radiate from your forearms to your upper arms and all across your back. Everything must be drum tight.

Duck under the bar and jam your shoulder blades as far back as you can. This should be uncomfortable.

The bar should sit on your mid traps, not the top of your spine or your neck.

By keeping your hands in a little closer you can create a bigger shelf for the bar to sit on. By close I mean 6-10 inches wider than shoulder width. If you have shoulder problems, this is not an option and you will need to grab the bar wider. Never grab the bar with an extremely close grip or extremely wide grip if you can help it. Moderate grip width is best.

Now, to engage your lats, pull down on the bar. You should feel your lats flare out to the side.

With your head straight, chest up and back arched, take a deep breath and hold it then unrack the weight and take two steps back.

Your feet should be a bit wider than shoulder width apart. Think of an athletic stance. For example- the stance you would play linebacker in or guard someone in basketball. That’s usually about the exact width you want your stance to be.

Before beginning your descent exhale and get into position. Now take a huge breath and fill your belly with air.

Hold the air in your abdomen, not your chest. Basically you want to push your abs out as far as you can while also bracing them like you’re going to take a punch. If you wear a belt simply drive your abs out into the belt.

With your chest up and back arched, you are now going to push out on the sides of your feet like you are trying to spread the floor. This doesn’t have to be dramatic; just enough to engage the hips and glutes.

To begin your descent, break at the hips by pushing your glutes back and then squatting down as low as you can go without losing the arch in your back and allowing your butt to tuck under. If your butt tucks under and you go into spinal flexion the injury risk increases dramatically and you lose a lot of strength. You need to maintain a neutral spine throughout. If you can’t you need to seriously work on your flexibility and mobility.

The goal is to be able to break parallel while maintaining a neutral spine.

One thing you need to remember is to keep your knees tracking your toes. So on the way down you need to consciously drive your knees out. Probably the best coaching cue I have heard that makes this easy to remember and grasp is that squatting takes place BETWEEN the legs, not above them.
Getting Out of the Hole

46 arnold schwarzenegger leg squat How to Squat ProperlyWhen you can get to parallel without spinal flexion the fun is just beginning. Now you have to get back up.

When coming out of the hole be sure to lead with your head, driving backward into the bar but NOT looking up. In other words you drive straight back into the bar but keep staring straight ahead. Don’t cock your neck back. This will make you weaker and throw off your form.

The chest should be high and you should drive your elbows forward and under the bar and push your hips forward while consciously engaging the glutes.

On the way up you need to keep that deep breath held until you are at least half way up. At that point you can start hissing the air out as if you’re blowing it through a straw. Never let your air out before that or let all of it out before reaching the top position.

Pause at the top, let all your air out, gather yourself, go through the checklist, take another huge breath and do your next rep. Do not do piston style pump reps when squatting.

Warmup
Run the Long Block
Gymnastic Warmup

Strength
Back Squat 1 Rep Max

Conditioning
5 Rounds
12 Single Arm Swings/Side
12 Locusts
30 Squats