When I think of story ideas during the daytime, I don't even write them down. Instead, I sleep on them. If I wake up the next morning and can still remember those ideas, and they still seem like strong ideas, then I start working on them more in my head. If I can't remember them, or if the next day I think they suck, then I abandon them. Simple as that. If the idea can't withstand a night of sleep without me forgetting or poo-poohing it, then it wasn't a good or interesting idea in the first place.
But luckily, I woke up feeling awesome about the 2 new ideas, remembering everything I'd thought about them and more. One idea is for a stand-alone book, the other for a series. My brain's already on overdrive, developing more details of these ideas. I'll probably begin a file for each of them today and start jotting down the details. Not actually writing the stories yet (it's Emerson's time now, you know?)--just gathering details, snippets of character conversation I'm hearing in my head, plot points, etc... I don't want to lose these little gems while I write Emerson.
One of the most comforting things for me as a writer is never feeling like I'm fresh out of ideas. Because I never am. Fresh out of time some days to write them, but never out of ideas. :)