I fall into the outliner category. Part of this is because I have no sense of time, and with no outline, I would have my detective being in two places at once and responding to clues before he finds them. Part of it is because I find it easier to write the story if there’s already a shape to it.
An outline is the writer’s armature. With the shape of the story laid out, the writer can concentrate on the details—emotions, sub-plots, and character development. Some writers use detailed outlines laid out with Roman numerals. Others scrawl out quick plots on the backs of cocktail napkins. Julia Spencer-Fleming writes until she “finds the story,” then outlines the remainder of the book. I use index cards, writing brief descriptions of the scenes I think I’ll need, each on a separate card. When I can’t think of any more, I put them in what seems to be a workable order and begin to write. The advantage of this method is that, as new ideas come to me, I can discard, replace, or rearrange the cards. My “outline” is in a constant state of flux.
Maybe it’s just a way of convincing my left brain to give up control, since I often find myself in uncharted territory. My muse calls out, “Hey, wait! I have a better idea!” and we’re off, strewing plot cards behind us like a trail of breadcrumbs.