A lot of the time the stories come and go quickly. They're the ones that don't get written, or only get written years later when something else triggers a memory of them. The ones that get written are the ones that stick. Something gets stuck in my mind, a seed of an idea, a germ of a character. It often takes time for anything to happen, but one day I'll realize that germ or seed has grown into something more. These are the ones that get written.
For example, the book I'm planning to write next came from a newspaper article I read a long time ago. Probably two years ago? Maybe a little less. It appalled me, so it stuck. It's taken this long for that initial idea to become anything else, but it's definitely taken root, and is growing steadily. The characters are coming into focus with all their foibles and eccentricities. I know how the book's going to end (which is pretty unusual for me, since I usually start somewhere near the middle), and I even know some of the things that will happen along the way.
No, I'm not outlining. That would be too far out of my chaotic comfort zone, but I do feel as if I have much more of an idea of the plot going into this one. Perhaps it's a result of the pacing issues I've been struggling with in Taillights. Maybe I've actually learned something through the process.
Where do you find ideas? Do they come to you fully formed, or do you need to work for them?