Step into the middle of the trap bar and stand with your feet hip-width apart. Reach down and grasp the handles of the bar, then sit your hips back, lift your chest and shoulders, keep your neck and head neutral to the spine. You should feel your hamstrings switch on as you set yourself into position, this should be the driving force of the movement.
Keeping your back flat, stand up by straightening your hips and knees to lift the bar to around mid-thigh height. Squeeze your glutes at the top of the move, before lowering the bar back down with control.