By the time I start something I've already thought about it for a while--mostly the characters, who they are, their backstory, what they need to come to terms with, etc. I'm not someone who only gets to know their characters through writing about them. And by the time I start I have an idea of what their emotional arcs will be, where I want them to get, and, in general time, what needs to happen to get them there. So then I consider the whole in a sort of three act structure, with something significant happening between each "act" that changes the course of things to some degree. Before I start I need to know what those significant events will be, to ground my structure. One I have those, though, I take it one "act" at a time, putting together a basic outline only for my current one. I usually take a couple days to think through things that can happen, ways they might fit together, the impacts they might have, how they drive things towards the next plot point, how they shape the emotional arc, and then I make an outline for that part. It's not too detailed, for each chapter mostly just place, an action or two of the characters', a couple things they say to each other, what those thing make them think and feel. I do one for each chapter up of the act, but they get vaguer the farther I go ("Alex confronts Laura, who reveals her past"), to be refined as I get closer. All of it is totally changeable. If a scene goes a different direction, and it feels right, cool, I'll go and change the course of successive scenes building on it. Sometimes I note this in the outline and sometime I don't bother. I don't even look at it that much. Once I get to the next act I repeat the process. Invariably, things will have come up during the writing I didn't consider at the start, which I can then work into the next part. So I suppose I go back and forth between the writing and outlining too. I couldn't do a full outline before starting, but I couldn't go without one. So it's something like driving in the dark, but with high beams.