Bar Over Mid-Foot
To perform your best squat and deadlift, the bar must be placed over your mid-foot. Period. When it's too far forward, your weight goes toward your toes and you move forward. When it's back too far, your weight shifts away from mid-line and your torso leans toward the rear and becomes too upright. Either too far forward or too far back will result in diminished strength and a less-than-optimal lift. When the bar is directly over your mid-foot, balance is best maintained while force is maximally transferred. If you start the lift ahead of or behind this position, you must expend more energy than necessary to correct the position and get into proper placement. (Your chance of injury also increases when the bar is out of placement.) So be certain to start the lift -- decent for squat and ascent for deadlift -- with the bar directly over your mid-foot; and try to maintain this position throughout the exercise. By doing so, your chance to perform your best lift is ideal.