Outlines are good for documenting the few ideas you already have. I usually include things like snatches of dialogue and anything I naturally come up with, nothing more. Then I start writing. Everything changes. Don't worry. Characters drive the plot and you should let the characters go where they want to go, regardless of what you want them to do. After writing a first draft, I organize the mess that I wrote. I might write an outline. I might print out what I have and make revision (particularly dialogue, scene transitions, things I need to foreshadow, pacing, etc) marks with a pen. I might scrap the rest of the plot having gotten a clearer idea of my characters. I go back and forth between steps until I have something I like. Then I show other people.