Open with a bang. Don’t dilly dally around! Your reader wants to know within the first few paragraphs who your main characters are, what context they are playing in and the root of the story.
Your story doesn’t need to have a linear time-line. You might like to start at the beginning and work through to the end, but consider dumping the reader right into the action for a more interesting read. Some stuff can be inferred, rather than explicitly detailed. For example “Peter leaped out of bed on Wednesday morning” is only exciting if Peter had been grievously ill on Tuesday night.
In a short story, you don’t have space to spare for words and sentences that don’t pitch in and contribute to the story outcome. Consider whether your descriptions are making an important contribution to the narrative, characterisation or atmosphere. If they are just sitting around looking pretty, rip them out and put in some hardworking words instead.
The best stories work towards a climax where maximum tension occurs. This point is usually characterised by conflict of some sort at about 70-90% of the way through the narrative.
The easiest stories to read and write involve physical or emotional conflict between two or more characters. The story resolves when the conflict is resolved.
Harder to write are stories that have characters experiencing inner emotional, ideological or philosophical turmoil. Inner conflict is triggered by external circumstances, and the story resolves when the character experiences a transformation.
The final few sentences are the writer’s opportunity to shape the reader’s reaction to the story. Do you want your reader to feel satisfied that everything is sorted out? Are you aiming to make your reader question their own beliefs? Or are you leaving the ending open so the reader (or another story that you write) can extrapolate their own ending onto the story?