I go with the 'whatever turns you on' gang. I write a 2-5 page outline of where I want to go, and sometimes I end up there, more or less. But new things happen on the way, which can actually delay the story as it appears in the outline.
One thing I find very useful is what I call a prehistory of the main characters - a sort of potted biography of how and why they got to where they are when the story opens. Quite often a lot of this will not appear in the actual story, but it helps me to understand the person, and know better how they will react in a given situation.
And the most important document I create is a detailed time line of the main events and subsidiary events, and that I have to update if something in the story changes, or I can tie myself in knots with things which happen out of turn. The time line prevents you, say, having a baby in three months or twelve months, helps you to keep track of birthdays, for things like being old enough to drink, drive, vote and do all the other things teenagers look forward to doing. It's not just a time line of events, in other words, but I have columns for the main characters where their age in years and months is calculated at each event.
Just now I'm working on a metatime line. I'm working on my third novel, in a series, where characters have major or minor roles in the various novels, and I have to keep track of where in the overall time line I am. Like A was x months pregnant at the end of book 1. How old is her child now, and what sex is it at the start of book 2.