Many players try to fix the common over-the-top swing by forcing their arms to stay to the inside, but most can't do it. A better way is to improve your footwork on the downswing.
An out-to-in downswing tends to get you up on the toes of your back foot too early. The only place the club can go from there is across the ball from the outside, producing a pull or a weak slice. If you can keep your back foot on the ground longer and still transfer your weight to your front foot, you'll have a much better chance of swinging the club from in to out.
Feel as if you're rolling your weight across the bottoms of your feet as you make your downswing. It should go from a flat back foot as you start down, to the inside of the back foot before impact, to the instep of the front foot through the strike.
The game has changed so much since 1981 (the last time the U.S. Open was at Merion), and everybody wants to see if such a short course by Open standards (6,996 yards) can hold up to today's bombers. My guess is, it'll be the best Open in a long time. Players will be able to make birdies and put pressure on the leaders instead of just waiting for mistakes.
Tips from: golfdigest.com