I agree with Simon on the value of looking at video of your swing. It's amazing what you see.

Here's something else you can try. When you swing, if you're making a hip turn, your right heel will start to come up at the moment of impact (if you're right-handed, of course). Make a point of watching for this in your peripheral vision. If you see your right heel start to come up, that means your head is still where it should be at the moment of impact. If you pull up too soon, you won't be able to see your right heel lift.

I used to have a very strong tendency to lift up and top the ball, but I rarely do it anymore (I have plenty of other faults, but not that one). This method fixed it for me completely.

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Todd
Philadelphia, PA
USA

The reason the pro tells you to keep your head down is so you can't see him laughing. ~Phyllis Diller