Found an interesting article on “micro fiction” on The Guardian:

Stories in your pocket: how to write flash fiction by David Gaffney.

I began to produce these ultra-short stories – sawn-off tales, as I call them – when I was commuting from Manchester to Liverpool…

…

These stories, small as they were, had a huge appetite; little fat monsters that gobbled up ideas like chicken nuggets. The habit of reducing text could get out of hand too; I once took away the last two sentences of a story and realised I had reduced it to a blank page.

…

How to write flash fiction

1. Start in the middle.

You don’t have time in this very short form to set scenes and build character.