I posted previously about my whacky left shoulder hitch on the downswing. But I have flaws that have exacerbated that problem.
My shoulders usually turn properly on the backswing, with my left shoulder moving DOWN under my chin and my right shoulder moving UP behind me (i.e., shoulder line maintaining a perpendicular relationship to my original spine angle). Note that the left shoulder should not point down early or it can cause the upper body to tilt toward the target; the left shoulder move across before pointing down. (Updated 1 Mar 15)
However, in an attempt to aid hitting from the inside and avoid an OTT (over-the-top or outside-in) move, I've developed a habit of having my shoulders see-saw on the downswing. In other words, the shoulders have too much up-and-down, linear shoulder motion with little to no rotational movement.
Therefore, my shoulder plane was rotating back correctly but changing directions and becoming too vertical on the downswing. It was going too much down and not enough around. This is the identical problem that Tom Watson talks about in his Lessons of a Lifetime; his right shoulder moved too much under and not enough around; his ball flight errors were pushes off to the right. He fixed it by feeling like he was coming OTT compared to what he had done before. For Tom this amounted to his "secret." It was his eureka moment.
In reality, the correct shoulder plane has the left shoulder pointing down toward the target line on the backswing and right shoulder pointing down toward the ball on the downswing; think of hitting the ball with the right shoulder--some call this "covering the ball" with the right shoulder.
The key move is to feel like the right shoulder on the downswing REPLACES the left shoulder's backswing position and points DOWN at the ball. In other words, the right shoulder must move DOWN, FORWARD, AND OUT. Too much of either isn't good. Keeping the head back behind the ball while using this motion allows one to hit from the inside instead of coming OTT. If the head (and spine angle) shifts forward with the weight shift to the left leg, this shoulder move will cause the swing to be OTT.
Another feel to go after is that the right shoulder stays higher coming through the ball; in other words, the shoulders feel more like that turning level to the ground (in reality they aren't). This provides a shallowing effect to the swing, resulting in a swing that's flatter and more "rounded" as opposed to "up and down."
The correct finish will have the right shoulder pointing at the target; if it's trapped behind the left in any way then the swing went unfinished--a stuck swing.
It's important to note that this is a feeling. With a proper setup, backswing, and throughswing, the shoulders will be only slightly open at the moment of impact. Because of the continuity of the swing's motion, the ball will be just departing and then the right shoulder comes through powerfully.
At the top, think of replacing your left shoulder with your right. That will help you turn through while keeping your right shoulder under your head instead of spinning out in front of you.
'MOVE THE RIGHT SHOULDER TOWARD THE BALL'
When I start down from the top, I try to feel as if my right shoulder goes directly to the ball, and this improves my swing path. Chuck also says this makes the body square the face at impact, which is more reliable than trying to do it with a lot of hand action.
If the right shoulder comes down (rocks slightly) as it begins to turn, it brings the upper right arm against the right side and the swing starts down on an inside line.
It is when the shoulders turn, throwing the right shoulder high and out toward the ball, that the golf swing goes outside. Keeping the head back helps the slight rocking action which brings the right shoulder down.
If the head comes forward at this point, we lose the tension and get ourselves, in a manner of speaking, "over the ball" as we hit it.
If we keep the head back we do in truth stay back of the ball where we should be.
The head must be set back as the golfer reaches half way down to ensure the golfer attacks the ball on the correct inside swing path.