Since I touched on this a bit yesterday, I might as well spend some time going over exactly how I write.
When I wrote my very first, very bad, novel at the age of 12, I did it from start to finish all in one go. It was hand written in green ink, which my generous and encouraging mother typed up for me. Many years and numerous false starts later, I managed to complete my next novel. This time the process was entirely different. I would write each individual scene as I thought of them, often from a paragraph to five pages long. They might happen anywhere in the story, and some of them might not end up working at all. When I had all of the main scenes written, I put it together, fleshing out the spaces in between. This process included a wall covered in cue cards with lines drawn between to keep things straight. It was pretty fun, but in the end I felt the plot suffered due to my lack of direction.
For the last two novels, including Magic High, I went back to my original process of starting at the beginning and working my way through the entire story until I reached the end. After finishing, I would rewrite huge chunks of the book, fixing any major problems before going back over the story for the fine tuning. Editing is the most time consuming part of the writing process for me. That's when I am forced to deal with plot holes, ever changing characters and other problems that I'd been ignoring. It took me a month to write Magic High. It's taken me three years to edit it to a point where I feel confident in calling it complete.
My current work in progress is a mash up of all the techniques that I've used for writing. Generally I'm focused on writing the story from start to finish, but often I end up hand writing a scene that will come much later in the story. Occasionally I'll still use a green pen, but more often than not, I'll just use whatever happens to be close by. Now if only I could figure out a way to use the wall of cue cards again. That was a work of art.