Squatting - knees over toes? page 3

[Wanderlust]

But the concentric portion is where stability is need the most.

[Iron Will]

Absolutely. So while expelling the air in the concentric movement you should be squeezing the abdominal wall and forcing the breath out of your body by contracting your diaphram. This increases abdominal pressure and allows the lifter to maintain an upright and correct posture. Its pretty cool. Its a little hard to do the first little while so thats why i just suggested to breath out on the concentric movement (I should have added forcefully). It does take some training because if youre not careful and hold your breath in the botom position for too long you can actually pass out. Thats never good :-)

[Danielfire]

Using a swiss ball between your back and a wall to guide the squat helps

[EvRevFit]

+1 to the "not really important" crowd. The way I see it, as long as your hips are doing what they should and your heels are firmly planted through the whole range of motion, you're good to go!