As a writer, ideas come from everywhere, all the time. Ideas for plots, world creations, characters, phrases, settings, you name it. It's a natural trait for writers, I think, to have their mind constantly trying to tell stories, looking for new stories, and putting together the pieces.
Earlier this week, I watched The Time Traveler's Wife with my wife, who has read the book. (great movie, and apparently, an even better book. I highly recommend them.) The moment the movie was finished, my mind was figuring out how to write a sequel to it called The Time Traveler's Daughter. (Ms. Neffenegger, if you read this and are interested in my ideas, let me know! :) ) Earlier today, my wife and I were talking about some random something, and she quoted a verse that got my brain kicking and out comes a wonderful concept for a multi-world creation that will be really fun to play with, when I get around to it.
That particular idea is what brings me to this post. Sitting at the table, laughing and discussing the idea over a pizza, she recommends I make notes, as we talk, on my iPod Touch, as I often do with ideas that I might be interested in dealing with, but don't have time for right now. (That would be pretty much all of them.) I delayed, concerned of getting pizza grease on my device, but regretted it later, when I was trying to make the notes and having to ask her what she recalled. I don't think I lost much, but it is an excellent illustration of how important it is to write things like this down. You never know when you will be able to go back and use something.
One of my unfinished novels, Thassodar Jax, which should be next in line after Hero Games (which should be back under way as soon as I finish Slave Princess, which is only a short story), was based almost completely from an image I had of the Texas highway system. I was driving home from class about sunset, and the way the roads lifted and twisted among each other made me think of them as almost organic creations, linear lovers entwined before the setting sun. This, in turn, became the way my protagonist saw the roads, being a stranger and seeing our world in a different way.
Children (my wife says like any man), will repeat behaviors that are validated and praised. Similarly, your mind will continue to search for ideas if you validate the ideas by writing them down for later use. Also, as I tell me students, having a list of ideas of interesting facts can be a life-saver when you're dealing with Writers' Block.