The golf swing is an arc, and the lowest part of the swing is the bottom of the arc. Much of the work and practice I've done over the years has been geared to producing a consistent bottom of the arc. It's a much misunderstood concept. Johnny Miller believes it's the most important lesson you can learn in developing a good swing. He taught it in a clinic I did with him, Arnie and Jack not long ago. I like it that we agree on this key point.
Every golfer should be striving for a consistent bottom of the arc on every swing. It's the primary element in a repeatable swing. It applies to almost every iron shot you play off turf (the driver and putter are struck slightly on the upswing). When we hit the ball fat (the divot starts behind the ball) or thin (the club hits too high on the ball), we are not finding a consistent bottom of the arc.
This is a major difference between pros and amateurs. The pros make "ball-divot contact," as Eddie Merrins calls it in his teaching. The bottom of the arc is ahead of the ball. A lot of poorer players hit the turf behind the ball or are otherwise inconsistent reaching the bottom of the arc--that's mainly why they're poorer players.
Here's how I practice hitting iron shots off the turf. I draw a line out from the middle of my stance. I put a ball down on that line, and I want my divot to start at the front edge of the line (right). The bottom of the arc occurs well in front of the line, not on it and definitely not behind it. The bottom of the arc is ahead of my stance center.
I'm using a 5-iron here, with my normal ball position for that club. Your ball position for a particular club might be slightly forward or behind the middle of your stance. I vary my ball position from the middle of my stance for different irons-- slightly forward for the long irons and slightly behind for the short irons--but not more than a couple of inches off center.
On the course, you determine the bottom of your arc with practice swings. Most people make practice swings they don't repeat with their real swings. And a lot of amateurs make a poor weight transfer and fail to get the club to the ball before they take a divot. The bottom of the arc is behind the ball instead of ahead of it.
If you've shifted your weight correctly on the downswing, your right knee should be pointing toward the ball at impact. If you haven't--and you hit off your right foot--the bottom of your arc will be behind the ball. You'll probably hit it to the right.
Use these tips to make better contact on all your iron shots.
From The Timeless Swing by Tom Watson with Nick Seitz. Copyright © 2011 by Tom Watson. Printed by permission of Atria Books, a division of Simon & Schuster Inc., New York, N.Y.