We all want better rotation, it's drummed in to all golfers. The better the coil, separation the more power we can produce.  So how can we do that just with our eyes?

The Key to the Keeping Good Form at the Top of the Back Swing

Whats it going to do for me?  Early extension is when your hips move forward towards the ball on your down swing. This will often make you come up away form the ball creating a hook or a block.