First off, I don't know if "inspiration" is the right word. It's more like compulsion. At its most extreme, a kind of expulsive urgency...
You know that feeling when you've got food poisoning, or a gastrointestinal bug, and you're not quite ready to throw up, but you know it's coming...? That's how it starts. There's something in me - something bugging me, occupying my subconscious processes, a psychological/emotional irritant - that needs to come out.
But I have no idea what it is...
And then it hooks something. Sometimes it's something I read. More often, it's a song or piece of music. (I'm a frustrated musician, at heart.) And then, like an oyster, I start internally shaping it around the unknown irritant, enlarging and and stylizing and polishing it with layer after layer of ornamentation, stirring in my own aesthetic contributions along the way...
And then it's ready to come out.
At that point, though, however pleasing, it's still just a disconnected mess of ideas (mine and others) with an, as yet, unseen and unknown psychological/emotional core. In fact, I'm usually halfway through a project before whatever irritant it was that really first inspired me becomes clear to me.
And that's when the real work starts...
Drawing out whatever it is I've been keeping from myself and threading it gracefully throughout the work, attempting to connect it stylistically and thematically with the other elements around it, discarding those that can't be assimilated into the whole.
Eventually, it acquires enough unity and clarity that I am content to abandon it as, "as good as it's ever going to get." Though, I'm usually wrong about that, and I'll sometimes return to something months or years later...
I suppose that's more a description of my process than a direct answer to the question, so I guess I'll say that my "inspiration" usually results from a synergy between some event or events from my own life and some external idea or ideas that happen to be floating around my immediate environment.
Probably a deeply unsatisfying answer. Almost as unsatisfying as whatever creative work I produce as a result of the above process... Well... Who says art has to be satisfying...?
@missy @rambo