I would start by developing a pre-shot routine. There's plenty of info. on this site and sites like this one for you to read up on.
Secondly, practicing tempo and balance are just as important, if not more so, than most of the mechanical swing drills out there. I like to think of swingly smoothly or swinging nice and easy. I hate the word slow. You want the club to go fast. And that's exactly what will happen when you swing smoothly.
Try reading up on and developing a consistent pre-shot routine and getting a tempo that would make ernie proud and most of the mechanics will take care of themselves.