Since this is my first book, I've been stumbling along a lot, but I did start with narrative outline--that's a narrative written in present tense that walks through the basics of the storyline. "Anna sees Tip and hates his guts... He flees from the ceanothus around the pine tree..." That sort of thing. BTW, I can guarantee you neither of those phrases exists in my book.
I have changed things a lot, giving a great deal of credit to what has to be the best writers critique group ever. Because of those changes in the plot, or in characters, the old narrative is pretty much gone, but some of the landmarks still provide a bit of a guide for me--like shadows in the fog.
I know that certain things have to happen at specific times, that I need to show my characters personalities through dialog and action that also moves the story forward, and I need to balance the "exposure" the reader gets to each character so that the more important characters get more page space than the lesser ones. Periodically I stop and evaluate these sort of things. Is it time to bring the hero back in? Is it time to reveal more about her father and the rift there? Is it time to put in another excerpt from the book that Anna, my main character, is writing? ( I do that here and there. I use it as foreshadowing or sometimes just as a parallel to what is going on in Anna's "real" life.) So I have sort of a story within a story. The excerpts are also often comic relief. Anna's fictional heroine is Cody, who is a six-foot bombshell lawyer who sometimes talks like she came out of a Dashiell Hammett book. She's not very nice, and is a lot of fun to write. Anna is, as one of my critique group says, "creative, repressed, tormented, and in trouble." I like her too much to call her neurotic, but...there's a lot of contrast between Anna and Cody, the bold character she's created for her books.
Steven King calls his writing "uncovering the bones"--gradually revealing your story as archaeologists do when they sweep away the debris at a site. That suggests his writing just unfolds. I don't believe he uses an outline as such, but I'm sure all writers need to know basically what direction they're going as they write. But what has been working for me is to let the story unfold from what ideas I have in my head, and if some other direction occurs to me in mid-scene, I may investigate it, write it out, toss it later, or refine it. So far, I've tossed out a couple of characters to allow more of the father/daughter thing, for example. But I do know pretty much the highlights of my story--what's coming up to cause some more tension, what's going to be an obstacle to a relationship, what's going to strengthen it in the long run. But a lot of the details pop up as I go.