Hip Rotation Drill [Pivot in the downswing]
This drill activates your hips which helps create separation between your hips and shoulders and helps keep your hands and arms from becoming too active in the downswing.
Here are the 4 key steps of the drill:
#1: During the downswing, you want your hips to be rotating open as the club descends toward the ball. At impact, your hips should be about 45-degrees open (your belt buckle should be pointing to a spot about halfway between your ball and your target).
Rotating your hips open also makes room for the club to come through impact and will stop any tendency to stand up out of your posture and flip the club into impact.
#2: Your trail foot is a key piece in getting proper hip rotation. Push off with your big toe to initiate the hip rotation and as you come into impact with the ball, the heel of your trail foot should be about an inch off of the ground.
If you don't loosen your heel and allow it to lift off the ground, it makes it much tougher to open your hips. Once your club has fully released (about 45-degrees in front of the ball), your trail heel should be even further off the ground (approximately 2-3 inches, or more).
#3: For this drill, take two practice swings and then one full swing for each rep.
During the two practice swings, bring the club back and then on your downswing, pause at impact. Here, check that your hips are open about 45-degrees and that your trail heel has lifted off the ground about an inch.
Once you've checked these two things, rotate on through and pause at the club's release point. Check to see that your club's shaft is splitting your forearms about 45 degrees in front of impact and that your trail heel is now about 2-3 inches off the ground.
Repeat this practice swing with the two pauses, and then finally take a full swing without a pause and emulate those feelings.
#4: Do as many reps as you need to get this feel to become natural. It may help you to place a 2nd golf ball about 4 feet down your target line as a focal point for your club's release.