I just re-read the entire script, making sure there are no typos. Then I double check by readng it backwards. It works, since all you're seeing is the words, and not trying to make sense of them.
Next, I say the dialogue outloud. While I'm walking my dog, I try to think of different ways to say something. And then I do a scene breakdown, figuring out which scenes don't belong, and which do. If I loose a lot of pages with deleting some unnecessary scenes, I write some more in a separate document, and then paste it in.
Finally, I go through my thesaurus to se if there are any other ways to say something in my action. Hope that helps!