I’ve recently read two good books by Elizabeth Lyon. I recommend them both. The first one is Manuscript Makeover. The second is Writing Subtexts. I think she has taken editing to a new level.
The first one has a great deal to keep in mind. I think the only way to use it is to go through your manuscript in several sweeps looking for different things on each sweep.
The second one is much shorter, but no less valuable. It helps you to write on a deeper level.