Thanks to a member of my writing class, I found a very useful post on Deadline Dames about outlining here.
If you've never tried outlining, I can't recommend it highly enough. The post on Deadline Dames shows a couple of fairly simple, straightforward ways to do it. One uses a fave of mine The Writer's Journey by Christopher Vogler to get things going.
Whenever my writing bogs down and I feel like I'm trudging through sludge to get something on paper, it's almost always because I have no idea where I'm going or why this scene exists. The answer is - outline! Every scene in the outline has a purpose, and knowing that purpose makes it ten times easier to write the scene.
Things will change as you write. You'll come up with ideas that never occured to you before, or see that things should go together differently. That's fine. The outline is not set in stone. I often reoutline, or jot notes in my old outline to indicate changes. It won't squash your inspiration - it'll foster it.