Stay in the Box
In order to maximize the power in our swing we need to efficiently "wind up" our body or core during the backswing. This concept has been known to confuse students and has resulted in either swaying or being afraid to move away from the ball going back.
A visual that I teach is to picture yourself in a box and as you turn back your chest will move over the outside of your right foot and as you swing forward your chest will move over the outside of your left foot.