This is the exercise that made John Cena the man he is today. You should squat hard enough so that you can walk out of the gym after squats and consider it a good workout even if you do nothing else. You should at least be able to squat your bodyweight to call yourself strong. Try to get to sets of 1.5 times body weight for some reps. John can squat with more than 550.
HOW TO DO IT: Grab the bar tightly, hands as close together as is comfortable and elbows pointed down-this will make sure your upper back is contracted. Come up under the bar, resting it on your traps, and lift it off the rack. Step backward, and stand with your feet a bit wider than shoulder-width apart and toes turned slightly outward . Take a deep breath, forcing your abs outward, and bend your hips back as far as you can. At that point, keeping the arch in your lower back, bend the knees to lower your body as far as you can (try to squat to where your thighs are below parallel to the floor) . When you've squatted as low as you can without losing the arch in your lower back, contract your glutes and thighs and explode back upward to the starting position, exhaling the breath forcefully. That's one rep. Do not let your heels come off the floor at any point.