A few days ago I thought up a pretty neat idea for a story (which I'm willing to take beyond the concept stage) under the shower.
I quickly stopped showering, hastily dried myself, brushed my teeth, and rushed to my computer to write it down. I thought I'd write a quick, short "proof of concept" kind of thing. It ended up being a full two pages long, and took me roughly an hour to write.
I went to bed way too late that night.
It's cool though, when you just get a rush of inspiration like that, when you think of something seemingly unrelated to your previous thought, repeat that a few times, and then you have a great idea "out of nowhere". Always fun to have those.
Same goes for brainstorming sessions. You just jot down anything that comes to mind, and later you filter out the crappy stuff. There's bound to be some gems in there, that get you going all "I normally wouldn't have thought of that, but it's most certainly something I can make something good out of!"
When/where do you get most of your bright moments?