How to squat
Set your feet, brace your core, move the bar straight.
Setup
Feet shoulder-width, toes out slightly. Bar on your traps, not your neck. Breathe in, brace like someone's about to hit you.
The movement
Sit down between your heels, knees tracking over toes. Drive up through your whole foot. The bar should move straight up and down.
Common fault
Heels lifting means the bar is drifting forward. Lighten the load and fix the path first.