Failing to control the club during the downswing is a potential cause for nearly every style of poorly hit golf ball, ranging from topping the ball or hitting fat behind the ball to balls that leave the target line. This is done either through a direct pushing or pulling at the moment of impact or through a swing that promotes a slice or hook.
Remain Natural Up Top
The best way to master the downswing is to first work on properly bringing the club back, and understanding that with the club in position at the start of your downswing, you've already done most of the work. Too many players over-think in their downswing, attempting to swing at the ball as hard as they can. This leads to erratic swings that cause the ball to travel off course, or one that hooks or slices once in the air. With your arms in the cocked-back position, the natural movements of your arms brought on by changes in your lower body will cause the arms to descend to the ball.
Start With the Lower Body
In order for the arms to react naturally, however, you must begin the downswing with your lower body, shifting your weight toward your front foot and turning at the hips. To shift the weight, slightly flex your lead leg, allowing your body to shift forward. While your head will be moving forward, it should remain level throughout the swing, traveling parallel to the ground. Once you have dropped your weight with a slight leg flex and begun to shift it forward, begin to unwind your hips toward the target. As your hips turn forward, they will naturally force the shoulders to follow suit, starting your arms' natural descent.
The No-Arms Drill
This is a practice routine designed to help golfers develop proper lower body movements. A golfer takes his usual stance but without the club. Each arm is brought up and in so that each hand is holding the opposite shoulder. The golfer then practices taking golf swings without removing their arms from their tightly clasped shape. As the arms are not extended and holding a weighty club, it is easier for a golfer to get used to the feel of letting the lower body do the work to generate forward momentum.