Clubhead speed for the average golfer is 85 to 100 miles per hour. Let's say you're swinging down at 90 mph, and your body stops turning . What happens? Well, you're not stopping that clubhead, so it whips past you. The face flips closed, and you hit a snap-hook--a low screamer that turns left before it leaves the tee box.
With most snap-hooks, there's another telltale sign: Your weight never shifts to your front foot during the downswing. Combine that with a stalled turn, and it's easy to snap it. I see this a lot on uphill tee shots, where there's an urge to hang back and help the ball up, or when nerves or fatigue work against a full turn through the ball.
Here's what I tell my players who are fighting the hooks: "Get your belt buckle to the target." Keep turning until the middle of your body faces forward. And be sure you shift off that back foot. Shift forward, turn through. You'll beat those nasty hooks.
Some players have too much body action on the downswing. They slide their hips aggressively, which can cause the club to drop behind the body. The result often is a big block to the right. Here's a drill: Take a narrow stance, and hit drivers at 75 percent. You'll learn not to slide and to make a better turn through.
Butch Harmon is a Golf Digest Teaching Professional.