I've never written something this long before, so I'm having to adapt. I do know I like to sketch out what I'm doing as I go, but that has often been just a few scenes ahead, rather than outlining the whole thing. I need a vision about what should happen in a scene before I really feel comfortable writing it, and I need to know how it's all going to end before I can effectively start. But I don't write sequentially, and I kind of do a rough cut of a scene, then go back and flesh it out. So while I guess I do have an outline, it's pretty much a sketch of what I think will happen, and I color in the bits that appeal to me as I go along.