A new addition to last week's discussion (see below). The next DE installment will also be up shortly.
I can't continue writing a short story until I get the first paragraph right. That paragraph establishes the voice, the tone, the mood, the rhythm -- in short, the world the short story will occupy. And of course the first sentence is the door that opens onto that world. An instructor of mine (or perhaps I read this somewhere) claimed that the first paragraph of a short story is the story in microcosm. I'm not sure this is always true -- some stories build slowly from unpromising beginnings -- but for me the best stories have opening paragraphs that function as the "unexploded metaphor" of the story (the term is Adele Wiseman's, in relation to poetry)
Whenever I bog down in a story, I go back to that first paragraph, and first sentence, to re-discover what the story wants to be. Finding the tone and voice and rhythm is key. I often read aloud to establish that rhythm in my head, though it has to be a subtle and improvised one, not a steady beat. The whole area of rhythm in prose is woefully under-explored by critics. For me it's an essential element in the story's scaffolding.