Good definitions can be enlightening in themselves. I came across this one in a writing class I took. I think it was the one taught by Joyce Allen here at the Carrboro ArtsCenter:
Story – a journey, actual or metaphorical, involving a person (or person equivalent) the reader engages with for whom something is at stake. The person finds problems and meets them in some way so that by the end something has changed.
What is at stake in your story?
What problems are you finding?
What changes might occur depending upon how you meet them?