I am a firm believer that great hitters and athletes of all disciplines have excellent footwork.  One of the essentials to a great swing is proper weight distribution.  When I talk to players I like to keep it simple by saying that hitting is basically taking weight from inside the back foot to inside the front foot.  I believe that hitting is not purely rotational, in fact, the upper body should not rotate until the lower body has shifted its weight into the front leg.  The swing has a linear weight shift after the stride which allows a player to "use their legs" to produce power.  The swing starts from the ground up and that energy and power is transferred into the bat.  Keys to a quality shift include:

1.  Weight going from inside the back foot to inside the front foot.

2.  As the front heel strikes, the back heel is moving off the ground and forward ("break the ice").

3.  The hands remain near shoulder height to create torque in the body (bat lag vs. drag).

4.  The chest of the player faces home plate.

5.  The front shoulder is closed (tucked in) with chin touching or close to touching it.

6.  There is a near 90 degree back arm and some bend in the front arm.