The problem: A loose, hands-dominated swing where the left arm doesn't stay in close to your upper body.
Simple fix: Expensive "swing jackets" will help you constrict your range of motion, but so will a credit card or an old glove. "Personally, I wouldn't spend a nickel on a jacket when a card is simpler and more effective," Goldstein says. "Place the card under your lead armpit. It shouldn't fall out until midway into the follow-through. This means that your larger muscles are playing the leading role – not your hands. Hit at least 30 full-swing shots this way at the range to start reprogramming your swing."