A golfer's hips and upper body should mostly pivot in-place, staying fairly centered with no lateral movement. If you're like me, you've struggled with a sway that moves the swing plane's low point all over the place, making it difficult to get back to the ball consistently and apply power efficiently and effortlessly. The body can sway moving right, but it can, unfortunately, sway too far left on the downswing--getting too far ahead of the ball.
At some point, I think a golfer MUST get this point to advance beyond high handicap status: The backswing pivot occurs on the inside of the right leg and inside the right foot (for right handed players). Now, you may have been told that before from many credible sources and thought you WERE doing it, but when you really learn to do this right, a major lightbulb will go on over your head.
If you discover that your right hip is moving outside of your right knee and placing weight towards the outside of your right foot, you are swaying. This is very subtle and sometimes difficult to catch. The hips and knees should turn inside the feet.
The right hip actually moves straight back and even inwards a bit towards the center of the stance; the hips and knees should always stay centered between the feet until the very end of the swing.
A drill that you can find throughout the internet works to teach this sensation: Simply place a golf ball underneath and to the outside of your right foot and take some practice swings. There are also more expensive training aids available that can teach the same feeling. See how the swing center (and therefore bottom of the swing) stays closer to where you established it at address? When you first hit some balls while concentrating on this move (when you've been a swayer), you'll immediately understand the difference.
When this is done properly, the outside of the right foot should feel like it's slightly off the ground during the backswing, and the right knee will kick inward toward the left knee ever so slightly during or just before the backswing. Some pros use the inward kick of the right knee as a way to start their swing, and it's not a bad idea--it helps remove the possibility that you will sway. Or you might consider just kicking in the right knee slightly and concentrating your weight into the inside of the right foot as part of your address procedure. This bracing maneuver concentrates the weight on the inside of the right leg where it should be, preventing a sway to the right during the backswing. As a result, ball-club contact is much more consistent and powerful, because no energy is lost trying to find the ball again.
But this can be taken further, because one should really be on the inside of the LEFT foot during the initial part of the downswing! Hank Haney states that the weight should feel, initially, as if it's moving from the inside right foot into the left big toe and then finishes on the outside of the left foot. Therefore, the left foot rolls from inside to outside during the downswing, while the right foot NEVER rolls to the outside on the backswing. Tiger Woods and Jack Nicklaus (two of the best players to ever hold a club) say that the game of golf is played INSIDE the feet! It's also easy to see how moving first to the inside of the left foot on the downswing can keep the head behind the ball where it's supposed to be at impact, instead of moving out ahead of the ball. But the kicker here is, you shouldn't TRY to stay on the inside of the left foot; just concentrate on staying on the inside of the right foot during the backswing (ensuring you maintain a flexed right knee) and the rest will take care of itself on the throughswing.
Achieving a centered pivot is possible when you recognize that the right hip does NOT move to the right at all during the takeaway: It moves straight back and even towards the body's center line, and the right leg stays angled towards the target (does not move towards a perpendicular-to-ground position). As a proper on-plane takeaway keeps the club head outside of the hands, the correct opposing move is for the right hip to move straight back. This thought should also keep you pivoting correctly.
Shawn Clement describes this feeling of playing on the insides of the feet as "bracing against a firm left side," because backswing energy is expended in making a centered turn, rather than wasting energy moving laterally backward and then forward again. Shawn says that any weight shift (back and then forward) is no more than a inch long! This is where the erroneous belief that the head doesn't move during the swing comes from: The head actually does move slightly right on the backswing, but it's such a small movement that the golfer doesn't always notice--it feels centered. Large movements to the right mean the swing bottom is moving well right of where it was set at address (probability to hit fat increases).
This works for ALL strokes: Drives, irons, chips, pitches, and even bunker shots (you can even dig the inside of the right foot into the sand to brace for those fairway bunkers, which helps pick the ball cleanly). For the short game and bunker shots, the weight on the inside of the right leg simply keeps one braced on the inside of the left foot (i.e., there's little to no rightward weight shift).
In an effort to keep your head still, your weight won't be able to shift to the right (for a right handed player) on the backswing unless you sway your lower body. This is not the way the tour pros shift their weight during the backswing.
Now, it doesn't take a lot of head motion to get your weight to shift, we measured it in centimeters. Most tour pros move their heads from 7 cm to 15 cm during a backswing.
Keeping your weight on the inside of the right foot during the backswing is critical to shifting properly. Allowing the weight to get to the outside of the foot doesn't give you a strong base to push off from when "springing" over to the left side. This can also lead to the dreaded sway, which results in a lot of wasted movement and is corrosive to good swing mechanics. To find a proper position, keep the right knee over the inside of the foot at address and throughout the backswing. Obviously, it's not good medicine to think about this during the swing, but stop at the top of the swing occasionally and check your position. In time, this will pay off in added power and more solid hits.
The key to proper footwork is weight distribution throughout the swing. Good golfers play within their feet. In other words, their weight is on the inside of the back foot on the backswing and on the inside of the forward foot on the through-swing. The average player constantly fights the weight-distribution battle, falling to the outside of one or both feet. The result is a loss of balance, control and power.