One thing I think would be nice about an outline is that you could see the shape of your story. That's very appealing. But since I discover my story as I write it, that isn't an option.
This time, however, I'm trying something new. (New for me, that is. I'm sure others have done it before me.) With 14 chapters now in hand, I'm writing something very much like a story treatment--those short narratives that describe the proposed course of a screenplay. These are invariably written in third-person present tense, and so I am doing likewise, hoping that the kazillions who have gone before me will have worn a path in the fabric of existence in which it will be easy for me to plod along.
What I'm doing is laying out the narrative with each chapter taking up a single, numbered paragraph. And, that now done, I'm using the white space beyond my current chapter to add notes about where it is going--things I now know are inevitable, things I'm toying with, things that might happen, questions to myself. The sort of stuff that used to show up in my little pocket notebook, but now laying out there as possible extensions to portions of the treatment that are already "in the can," as Hollywood has it.
It's far from a pre-writing outline, but I'm finding that it's nice to be able to scan the shape of, as the Prince Valiant comic strip used to say, Our Story So Far.
Perhaps I'm just fuzzy-minded, but I find that when I'm in the middle of a novel and think back on what I've already written, I don't have much sense of the proportions or patterns the plot is following. This gives me a little bit more of a clue.
Those authors of more stable mind probably don't need to be reminded of what they have only recently written. It seems that I do, and this little "treatment" is what I'm trying for the moment. If that doesn't work, I'm going to try the tattoo approach used by the fellow in Memento (see photo).
I'm hoping I can get by with my current methdology, as the tattoo approach could get expensive.