If you read Brian's article on the Perfect Pivot and then practise it in front of a mirror it will help you quite a bit. Additionally, I found practising hitting balls with my feet close together kept my hips from sliding side to side as you would lose your balance if you did. Other thoughts, make sure you set up properly with the right amount of axis tilt and I found by intitiating the backswing by "sliding" a little bit towards my back leg (only about an inch or so), while maintaining the axis tilt set at address kept me from sliding just the hips and reverse pivoting. Hope this helps. I'm still trying to get this right myself.
