Starting Position: Step under the bar in a split-stance position (one foot in front of and one behind the barbell). Grasp the bar slightly wider than your shoulders with the palms facing forward, elbows bent. Position the bar behind your head either: (1) High along the top of your shoulders at the base of your neck, or (2) Low across the back of the shoulders, requiring a slightly wider grip. Do not allow the shoulders to shrug.
Brace your torso by contracting your abdominal/core muscles to stabilize your spine. Keep the chest lifted, and your head tilted slightly up. Dip slightly to unrack the bar; then straighten your hips and knees to lift the bar.
Take a step backwards and re-position your feet shoulder-width apart, side-by-side, with your toes pointed forward or slightly outward. Shift your weight over your heels.
Upward Phase: Exhale and slowly raise your heels off the floor, allowing your entire body leaning slightly forward to maintain balance. Do not lose your alignment, especially in the hips and low back. Keep your knees straight and abdominals strong. Continue rising until your weight is on the balls of your feet. Hold this position briefly.
Downward Phase: Inhale and slowly lower your heels back to the floor. Shift your weight back into your heels and stand up tall.
At the end of the set, step forward into a split-stance position, dip down and re-rack the bar.
Technique is very important in this lift. The tendency is to arch the low back during the upward phase, increasing the loading upon your spine. Use a mirror for feedback, and squeeze your abdominal muscles and glutes to help prevent arching.