Golf courses built on rolling terrain can be spectacularly beautiful but they also create treacherous downhill and uphill lies for golfers. Hitting from a severe downslope is one of the most challenging shots for many amateurs because your stance feels awkward and you fear not being able to hit the ball squarely. The result can be an off balance swing and a topped shot.
Select a higher lofted club than indicated by the yardage. The slope has the effect of reducing the loft of the clubface, producing a lower shot with extra roll so the ball will travel farther than your normal shot with that club.
Play the ball farther back in your stance -- 1 or 2 inches -- than you would if the lie were flat. This allows you to strike the ball when the clubface reaches the bottom of the swing.
Shift the majority of your weight to your back foot to maintain your balance.
Drop your left shoulder to create a spine angle perpendicular to the ground.
Strive for a slow, smooth swing that allows you to maintain your balance. Sacrifice distance if need be to keep from losing your balance. You may have to restrict your body turn somewhat, swinging more with your arms.
Stay down over the shot as you pass through the impact zone. Don't let your hands come up too quickly -- keep them going low as though following the line of the slope. In his book "Golf My Way" Jack Nicklaus recommends using the mental image of "chasing the clubhead out after the ball" as the club passes through the impact zone.