One of the major challenges in golf is to play the ball where it lies. Sometimes you will face a shot with a downhill lie, requiring several adjustments in your balance if you want to hit an effective shot -- and stay upright after you swing.
Difficulty: Moderately Challenging
Alter your stance when you are over the ball on a downhill lie. Your left shoulder needs to be below your right shoulder, and most of your weight should be over your left foot so you don't lose your footing when you swing.
Play the ball back in your stance, about 1-1/2 ball lengths closer to your back foot than your front. However, if the lie is extreme, you may have to play it even farther back.
If you're right-handed, aim your ball to the left of the target (to the right for lefthanders). Your ball will fade because of your downhill stance, so you must compensate by aiming to the left. Take about one club length more than you would normally use for a shot of this distance: If you would normally use a 5-iron, use a 4-iron so you don't overswing.
Hit the ball with a compact swing. You are not going to take the club as far back nor are you going to follow through as much as you normally would. Your weight shift will be less pronounced as well, since so much of your weight will be on your front foot throughout the shot. Your backswing and follow-through should be about half of what they normally would be.
Swing down along the angle of the slope so you don't the ball "fat" by taking too much of the ground behind the ball before impact. It will feel somewhat awkward, but will lead to an effective shot.
Tips & Warnings
Don't try to overpower the ball with a downhill lie or your could lose your balance and stumble.