My 14 year old son has a problem where he opens his front side too soon and his hands tend to drag. I have had trouble finding an easy way for him to stop from doing that. Recently I have noticed with most every good hitter that when the back knee begins it's turn the hands should begin to move forwards as well. So, I am telling him to pretend his hands are connected to his back knee and when the back knee starts to turn, the hands starts to go.