The single most common reason for not accepting a story submitted to us is the lack of plot. So, here’s just a quick response to the question of what do we mean by plot.
The question I would ask in reading is, when I’m finished, was I able to identify the conflict and see it resolved? Conflict, internal or external, is one of the primary elements in plot.
Characterization is another. Is this a person we can recognize, rather than the fictional equivalent of a blow-up doll? If it could be anyone, then it’s generic. Generic is boring.