My writing group frequently discusses whether it is better to outline first and write later, or write first and extract an outline from the writing. There certainly are contradictory opinions among successful writers. Stephen King says he starts with a submerged fragment of an idea and uncovers a novel through writing; he equates his process to an archeologist uncovering a dinosaur bone-by-bone with soft brushes and dental picks. On the other side, the outliners claim to increase their productivity and quality by orders of magnitude when they outline first and write later.
I don’t know. Stephen King is certainly productive. As Anthony Trollope described writing in his autobiography, his method was similar to Stephen King. He started with an idea and wrote from there. Trollope was exceedingly productive. He wrote his novels from beginning to end and seldom took time to revise before publishing, pumping out several books a year, and still working daily at the British Postal Service. (He invented the iconic British cylindrical letterbox.) There are flaws in some of Trollope’s novels—the same character might reappear with his name spelled differently–but most of his books are well structured. Rex Stout wrote like Trollope—from beginning to end with little revision. And his complex plots depend on clues planted early in the text.
For my own fiction efforts, I write detailed outlines and ignore them. My imagination never goes the same way twice. The best I can do is keep a running commentary on where the story might go next. I use the commentary to try ideas. I think the outlines and commentary helps, but not directly. When I am writing non-fiction, I write an outline form using the free open-source mind mapping tool, FreeMind. Mind mapping tools do no more than an outline, but the presentation helps me keep the whole in proportion. When the outline contains everything I want, I revise the outline into ordinary text. Works for me.