Learn to relax: Tension in the arms leads to a restricted swing. To relax your muscles, pump your elbows in and out at address.
One of the positions power hitters and great ball-strikers have in common is an easy, athletic setup. Relaxed muscles produce speed and fluidity. Tight muscles slow things down and restrict the body's range of motion.
Tension in the arms is a common problem among amateurs. To combat it, I teach my students to lighten their grip pressure and to develop a "soft-arm waggle." This gentle pumping of the elbows in and out (toward the chest and back out) breaks the chain of tension that can run from the shoulders to the hands. If you watch old videos of Snead and Hogan, you'll see they did this beautifully, as do many players today. It's the best way I know to alleviate arm tension so you can swing the club freely.
Jim McLean, a Golf Digest Teaching Professional, is based at Doral Golf Resort & Spa in Miami.