On the driving range pick a target. Be sure to set up properly to the target. Place the tee ball forward in your stance by 1 inch from where you normally set up. This forces you to reach for the ball, thus increasing your extension. As you improve your extension, you can continue moving the ball forward. You are now being forced to reach for the target, therefore gaining more distance because of the extension.
Improvement: This drill is very hard at first. If you are patient and keep practicing you will see great results.
Related tip: The same drill can be used with other woods and long irons. You may not want to sue a tee with the irons.