Two fragments that gell; an episode or phrase too good to be wasted; something written in an extreme of emotion just because you want to write; a character who takes over the story; a plot; an exercise. Yes, any of these. Sometimes they grow organically, sometimes they grow by accumulation, material added from trawling notebooks or doing research. A new sensation may emerge from inside the text as it grows. Maybe the initial idea can be thrown away now that the text has found its real purpose.
In the PEN/O'Henry 2011 anthology, Jim Shepard wrote that his piece "began as many of my stories begin lately - with my browsing around endlessly in an utterly nerdy and bizarre subject and then finding my imagination caught by a particular moment that resonates with me emotionally in unexpected ways". That happens to me as well - how artists have used sunflowers through the years; Pink Floyd's legal wrangles; how the legal status of protesters living in trees changes when a letter's delivered to them.
Alice Munro wrote "The stories that are personal are carried inexorably away from the real. And the observed stories lose their anecdotal edges, being invaded by familiar shapes and voices. // So one hopes, anyway". I use a mix of personal and anecdotal material. Yes I've been to Prague, and a school-friend has died. No, I've not seen inflatable pigs. I've stayed in a caravan, but that's the only personal part of the person-centred "The Big Climb" story where two people fail to connect with each other while learning about an absent third person. There are quite a few absent third persons in these stories.
In general I find prose much more of a reality-guzzler than poetry is.
If you can't change, move. AL Kennedy, amongst others, uses rooms and cities to represent identity. Journeys are traditionally quests. She often uses trains, but not as quests. As one of her traveling characters says, "You can relax here - this isn't anywhere. Whatever happens outside, there's nothing we can do about it right now". Kaye Mitchell says of Kennedy that her trains are "free of the expectations and judgements of others, a space in which to meditate freely on the past and her possible future". In many of my stories a person journeys (often by train) to make sense of something.
If you can't move, make the most of your stillness - find a form. Elsewhere I've used some tight forms. Here they're much looser, as in "Fractals" and "Definitions". Symbolism can become structural as in "Doors and Windows".
Suppose a text were just the symbolic lines? The white space surrounding such a piece might, like wet blotting paper, absorb the effects. Suppose the symbolic lines ended a non-symbolic story? We'd have a lyrical, enigmatic ending where the energy rebounds off the other text then is projected into the future, the white space beyond the writer's control. Why not embed the symbolism so that the surrounding text becomes infused? Why leave the best bit to the end?
In the Guardian (14/5/12) David Gaffney wrote "Make sure the ending isn't at the end. In micro-fiction there's a danger that much of the engagement with the story takes place when the reader has stopped reading. To avoid this, place the denouement in the middle of the story, allowing us time, as the rest of the text spins out, to consider the situation along with the narrator, and ruminate on the decisions his characters have taken". Maybe I do that too. In "Doors and Windows" the pretentious main character says "A father's a son's window. A son's a father's door". He receives no reply, but the influence of that symbolism is supposed to seep back as well as forth through the work.