Two problems mentioned in the posts above: (1) too much inside out, (2) not squaring the clubface resulting in pushes, are really the same problem and likely have the same cause. From my observations they are caused by the lead upper arm separating from the lead upper chest. If the arm and chest were to remain connected, the hands would come around the body more through impact, moving "level left," causing an inside to square path that John mentions above AND a square club face.

The hands do not move out to the ball or down the line, in the impact zone, they move left. Place yourself in the pre-impact, 6/100ths position, where the hands are in front of your right thigh and the shaft is parallel to the target line and the ground. Now, move your arms either out to the ball or down the line, very slowly. You will notice that the face is wide open. (inside OUT pushes) Then, from 6/100ths, allow your arms to move left of a line parallel to the target line and you will notice that the club face squares up. The arms moving left squares the club face, not the hands.

IMO, it is 100% unnecessary to THINK about a body rotation or a weight shift, as you start the downswing. This happens incidentally if you hit DOWN on the ball. Your brain subconsciously anticipates the downswing before the backswing is completed and causes the lower body to begin some forward motion to stabilize the body in anticipation of the upcoming motion of the arms. If you focus on making John's "Magic Move," and I really think that it is magic, of moving the hands BACK first, you will get the shaft ON PLANE and all the body shift and natural rotation you need, without ever having to CONSCIOUSLY think about it. The shot of the start of my downswing in post 21 above where my hands and the shaft move BACK to my shaft axis plane immediately, is what I work on each time in practice and is why I normally hit the ball pretty straight.

If you get John's tape and see his ARC or LINE of approach idea, you will also see that his magic move is almost happens incidentally as well, if you just focus on making the club head move over the line of approach. On a few occasions when I have been asked to help some golfers with their swing, I draw the line of approach on the ground or use masking tape on a mat and simply have the golfer swing over it. Almost instantly an over the top swinger becomes an inside swinger and when they see this on video, their jaws drops. I neither know nor work for John but his approach is simple and simply brilliant. The tape and/or the book, "The Secret of the Golf Swing," will help.