The halfway back stage of the swing is a good reference point and easy to practice.
The shoulders have rotated about 45 degrees (half their turn) and the left arm is level with the ground. The shaft should point down to the line of the ball and target and be at right angles to the left arm. The shoulders are rotating around the angle of the spine which is why the left shoulder is lower than the right. The hips have really done nothing except respond to the upper body, there has been no lateral movement and they have turned minimally. Both knees are still flexed.
From this point the shoulders complete the back swing by rotating to the fully turned 90 degree angle.
Since the wrists have hinged we simply do no more with them, they must be allowed to respond to the weight and momentum of the club.
Practice this drill with the use of a mirror. As with any drill the purpose is to teach the positions to occur instinctively, do not force this position while playing, simply practice the drill and let it happen.
Terry Gingell is a PGA Class A Professional. He's now taking signups for junior golf camps and adult group lessons at Empire Ranch and Genoa Lakes. Call 690-7970 for more information.