Writing is rewriting. We've been told this hundreds of times. The first drafts is just the beginning. There will be a second, a third, possibly a fourth. Plot points will change, scenes will be deleted, characters will be killed off. For me, this is the part of writing I dread. But I've gone through this process enough to learn a few things.
Get some distance. You cannot finish draft one and immediately go back to the beginning and begin draft two. You're too close. Put the book in a drawer for a few weeks, even a month. If you remember your work too clearly, you won't see what needs to be changed.
Cut, cut, cut. It's been said so many times, it's probably cliche: kill your darlings. Those beautifully written scenes, the ones that aren't really forwarding the overall plot, get rid of them. If it makes you feel better, put the deleted scenes in a file folder, just in case you need them. But you won't.
Add, add, add. Often times we are so roped up in the writing, that we forget to add texture to a scene. Look at the sections that are mostly dialogue or action and add description, internalization, depth. Even action sequences deserve to be slowed down and described; it often makes them more suspenseful.
Play with Structure. The order of chapters is not set in stone, nor is the timeline of your story. Don't be afraid to switch events, switch chapters, or change the major turning points. Sometimes a first draft is more like a 400-page outline. You're working out the structure of your story, and in the end, it may need to be changed.
Get feedback. During the revision is when you really need your critique group or other first readers. It's very easy to get stuck or to not know if something is working. Talk it out with your trusted readers, give them portions of the revision to read. The feedback won't only help you see needed changes, it will give you motivation to keep going.
Feel free to leave your own revision tips. We've all been there and if you're like me, it can be a stressful/frustrating part of the writing process. But in the end, you'll have a better book, which makes all this craziness worth it.