I've been asked a number of times where I get my story ideas from. Given that most of my writing is about the paranormal, speculations vary from my being a closet Believer (I'm not) to my having been dropped on my head as an infant (I wasn't).
The fact is, for most of what I write, I really am at a loss to explain where the idea originated. There are a couple of exceptions, of course. My novel Adam's Fall was inspired by the (true) story of Kaspar Hauser, the German "mystery child" of the early 1800s whose strange appearance, and even more peculiar murder, are still being discussed today. My current work-in-progress finds its origins in the urban legend called Slender Man (if you don't know about this creepy cryptid, you can read my blog post on the subject here).
But most of the rest of 'em came from who-knows-where. Often, it starts with an image; usually a single, powerful visual image, which I then dream up a story to explain. For example, my short story "Retrograde" began one evening with my suddenly visualizing a young woman standing behind a counter in a deli, who sees a total stranger walk in and begins to cry. My novel The Hand of the Hunter came from picturing a woman with a flashlight, searching in an abandoned house at night. Periphery started with someone seeing a little scaly monster out of the corner of her eye -- and the monster turns out to be a tree branch.
None of this, of course, is any closer to explaining where the ideas actually come from. When writing is going well, it often feels like I'm channeling something; that the ideas are coming from outside. Now, mind you, I don't think this is really what's happening. It's just what it seems like. Moreover, when that doesn't occur, my writing seems to take twice as long and comes out half as good.
I find creativity a peculiar thing. The idea that somehow, I am able to take my experiences, thoughts, and feelings, and without any particular conscious volition distill those into a single image, and then use that to develop a story, seems a little like alchemy to me. Perhaps this is why outlining, or using storyboards, has never really worked for me -- my best writing seems to happen fluidly, and to take me in directions I never expected. As an example of this latter phenomenon, in my novel Convection, the character of the convenience store clerk Jennie Trahan started out as a minor player, a snarky and saracastic foil for the point-of-view character's steadfast compassion. Jennie, however, didn't see things that way. The only way I can explain it is that about a third of the way through, Jennie wasn't satisfied with her part and decided to write herself a starring role. And I let her. Perhaps because of this, I've been told that she is one of the best-drawn characters I've ever written.
I've talked with some fellow writers about this phenomenon, and it seems that I'm not the only one who has had this sort of thing happen. None of this, of course, explains what is actually going on in the brain, or identifies where these ideas are really coming from. It does, however, point to a common experience amongst writers of fiction, and that by itself is pretty fascinating.