If you find yourself thinning shots or just not making solid contact in general, one of the most common culprits is inward extension. The term refers to the lift action that occurs as you’re making your downswing. Instead of maintaining your posture throughout the swing, you straighten up and move your hips forward.
Thankfully there’s a simple and effective drill for getting it corrected, and all you need is a wall. Get into a stance and let your hips rest against the wall, and with your arms folded across your chest, rotate as if making a swing. If you’re a righty, you should feel your right hip touch the wall during the backswing, and then as you rotate you should feel both hips making contact with the wall. Then, as if making an explosive turn in the downswing, focus on feeling your left hip press into the wall. This sit-down move will help you maintain proper balance throughout the swing and create more torque with your lead leg.