Certain pieces of advice depend on squatting style (high-bar vs low bar, wearing Oly shoes vs Chucks/flat shoes, stance width). Generally, though you want to take a big breath into the stomach to help stabilize your torso and lower back, keep tension in your arms and upper back, break from the hips first, push your thighs/knees out as you descend, and push from the whole foot with a little more emphasis on pushing from the heels and the outside of the foot.

I would say watch some videos of great squatters, especially ones who have a body type and leverage base similar to you. Example: 2 lifters can both be 5'10" and 220 pounds, but one might have a long torso and short legs, and the other may have a short torso with long legs. These things affect stance width, whether high or low bar would be more productive, etc.