Ah, this is how it goes: type out some shit, stare at it, delete it, rewrite it, stare at it, go trawling for images (Oh, sorry, Allen: shopping for images), find things, nothing really works, and then. BAM. You see something and it does that thing where it flips that switch in your head and then you have a story. Or, at the very least, a character. Or a character doing a small thing which might be the beginning of a scene.
Or, you know: "Sometimes I start with a letter..." Cue vomit and sadistic commentary over beers.