The most mind blowing drill I've ever done was as follows:

Grab your 8 iron (or 7 or 6 or 9, whatever you're comfortable with.

Put the ball back in your stance - middle or even further back. Make sure you're doing something so that you know that the ball is back (clubs on the ground or whatever).

Address the ball. Set your wrists (so cup the right) and so the club stays on the ball (ie don't let the clubhead come insiide - break your wrists so the clubhead stays on the target line).

Now, turn through.

Simple, isn't it?

It seems impossible to hit the ball this way - holding that wrist angle and simply turning, but it works. You get this low, piercing trajectory that spins. After a couple dozen balls it may help to put a tee in the ground 3" in front of the ball, and focus on making sure you dig out the tee. You'll start to hear this 'sproing' sound that lets you know that you're compressing the ball.

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True Length Technology Fitter - www.truelengthtechnology.com
It's live! - www.ShipShapeClubs.com
PCS Class 'A' Clubfitter

A new highlight: Golfing the home course on Christmas Day.

I say it too often: If it's golf club shaped, you can play with it.

For the record, I'm a club doctor, not a swing doctor.