Coming up on November, so NaNoWriMo time again. Here is an interesting set of posts on whether it is better to plan out one's novel in detail, or to just start writing and see where it goes.
On planning: http://theaccidentalnovelist.wordpress.com/2012/10/12/weekend-workout-prepping-fo-nano-or-not/
On just going with the flow: http://theaccidentalnovelist.wordpress.com/2013/10/30/nanowrimo-2014-team-pantser/
I'm usually some combination of both. I often have an idea that has been perculating in my head for years, often decades, where I have daydreamed various scenes here and there while walking the dog or shoveling snow. So I have a general idea of what the novel is about, who the main characters are, and where the novel is going, but with really only fragments of scenes here and there and big gaps between. No real structure or outline. So NaNoWriMo is a chance to get what I have down on paper and to see if I can connect the dots. The end result is often very different than where I started, and I occasionally write myself into corners by writing blindly; but on the other hand, I often generate new scenes and characters I would never have thought of if I were using a disciplined outline. By writing myself into corners, I force the protagonist to come up with a way to extricate himself, which I would never have thought of in an outline, because I would have known better than place him in that corner in the first place, if I had had a plan. So my hero is much cleverer and a much faster talker than he would have been otherwise.
It's true that I have had to cut whole sections of the novel that haven't worked out, because by going in that direction I precluded something that I realized had to come in later for the novel to work, or that went against character, or otherwise didn't work out. But at 2000 words a day, I could afford to dump a ten or twelve page section and try again; whereas if an outline had called for that scene and it had taken me a month to write, I would be far more reluctant to give up on it, persisting to the point of such frustration that I might be tempted to abandon the whole project as undoable.
I'm also quite a slow writer and tend to write longish novels, so has taken me two to three NaNoWriMo to get first complete draft. Now is the time for outlining, to make sure that I haven't lost track of any of the bits I started with (I lost two of the main characters there for awhile, and had to go back an account for their absence) and that everything works logically. I was actually surprised to find that my subconcious had indeed planted many of the clues in early chapters to foreshadow the unfolding of the mystery, even though I had had no idea what that mystery was when I set out. So having a first draft, I can go back and get a plan for the revision; I can use what my subconscious provided as raw data and use the resulting outline to tighten everything up so that the structure really works.
Or at least, that's the plan. Come Friday I start work on my new novel (opening scene clearly in my head, though getting that scene down on paper is a whole other thing) so will have to see how far on the back burner the previous novel gets pushed.