Stance should be slightly wider than shoulder width, toes pointed diagonally out. Engage your core as you sit back into a chair, drive the weight through your heels in the floor as you come back up to standing position.

Beginner: Try just the bar first or dumbbells
Intermediate: 15-35lb plates on each side of the barbell
Advanced: 40-60+lb plates on each side of the barbell

*Modification: do this squat with dumbbells