Follow the slope: To hit it flush, try to chase the ball down the slope with the clubhead.
My experience is that you seldom see a flat lie in the Masters. The downhill lie you get if you lay up at the par-5 15th hole is a classic case. I lay up there a lot these days, especially into the wind.
How do you play a shot from a downslope? Swing down the hill. To do that, widen your stance and position the ball farther back, with your shoulders parallel to the slope. If you're right-handed, your left shoulder should be lower than your right.
Now the important part: Your weight should be braced on your left foot. A slight weight shift to the right going back is fine, but your center of gravity should remain left of center throughout the backswing (on your left instep).
The tendency is to tilt back and hit behind the ball, so focus on hitting the ball first and taking a divot in front of it.
Because the shot will tend to fly lower and run more, pick the club up quicker with your right hand and make a steeper swing to get more loft. On shorter shots, I'll even open the clubface.
More Thoughts From Tom: What was I thinking on that four-foot putt I made to beat Fred Couples at the Mitsubishi in Hawaii back in January? KISS -- Keep It Simple Stupid. Head still, good rhythm, hit it solid. On short putts, I keep the face aimed down the target line as I swing the putter back and through. This helps ensure the putter isn't slightly open or closed at impact, which would likely cause a miss. With a square face, I can concentrate on speed and the correct line.
Tom Watson is a Golf Digest Playing Editor and the golf professional emeritus at The Greenbrier, in White Sulphur Springs, W.Va.