Fence Drill
Here is a drill that will help you to get the right feel for the proper path of the bat to the hitting zone.
Remember, all of the essential fundamentals must be adhered to: grip, stance, pre-swing, rhythm, etc., during this drill. Stand facing a fence, holding your back arm straight out so that the tip of your fingers just touch the fence.
Now, with bat in hand and utilizing the proper fundamentals, swing the bat through the hitting zone, concentrating on taking your hands "to the ball". The tip of the bat should not hit the fence. If it does, you will get immediate negative feedback.
Hitting the fence is a result of "casting" or "sweeping" your hands through the hitting zone. Take the hands directly at the ball (an inside path) hit against a stiff front side, and bring the wrist action into the swing. Finish high and over the front shoulder, your belly button facing the imaginary pitcher.
A coach needs to watch to make sure that the batter doesn't lean away from the fence or tuck in his elbows to execute this drill.