Select a weight that you're able to use for six to ten reps with strict form.
Assume the starting position, with your shoulders under the pads.
Center your feet on the foot plate, keeping them flat and pointed straight.
Adjust your foot position; your feet should be 1 to 2 feet apart.
Reach up and grasp the handles, with your eyes focused straight ahead.
Release the weight by moving the handles out as far as you can.
While holding the handles lightly, very slowly lower the weight; your thighs should be roughly parallel to the platform when you stop. Never squat any lower than this or you'll risk injuring your knees.
While keeping your feet completely flat, slowly extend your legs.
Stop once your legs are extended to roughly three-fourths of a full movement range.
Lower the weight again promptly (you should not rest or pause at this point).
Repeat until you reach failure (you can't perform any more reps with strict form).
Other Key Points and Reminders
At all times during this exercise keep your knees aligned with your feet. Don't ever bow or spread your knees, and make sure your feet stay flat.
Keep your lower back flat against the back pad at all times.
Do not rest keep continuous tension on your thighs!