The first tip is to go to your writer's group to get around other writers and help get the creative juices flowing. If you aren't a member of a writer's group, maybe you should join one. Another idea is to take a quick break from your current projects and write something short, fun, and silly to just get some words down on a page that don't matter. Or write a short story in a voice, style, or perspective that you don't normally use. If there's a Convention running nearby that has a literary track, you can go there and interact with writers on a larger scale, and maybe learn something that will help you refocus on your current projects. And if those tips fail, then try giving yourself a deadline with a fantastic reward for achieving it (I have found that bribery works quite well for me). But most importantly...
Keep Writing and Edit On