Begin with the barbell supported on top of the traps. The chest should be up and the head facing forward. Adopt a hip-width stance with the feet turned out as needed.
Descend by flexing the knees, refraining from moving the hips back as much as possible. This requires that the knees travel forward. Ensure that they stay align with the feet. The goal is to keep the torso as upright as possible.
Continue all the way down, keeping the weight on the front of the heel. At the moment the upper legs the lower legs reverse the motion, driving the weight upward.