Bashing the background on the head!
When you’re writing a short story, it’s easy to get sucked into telling the reader too much about your characters’ backgrounds. This slows the pace of the story down. The reader wants a story so it’s important to only include any background information that’s essential to the story. You only have a limited number of words for your story anyway so every word has to count. Be ruthless. If it isn’t necessary, don’t include it e.g.:
If you open a horror story with a young woman on the run from zombies, yes the reader will want to know how she found herself in that situation and the events which up to that point but the reader doesn’t need to know that the woman had a pet rabbit when she was five, once saw a glimpse of Robbie Williams in a supermarket car park and buys her clothes from M and S.
That is, unless it’s crucial to the story and pet rabbits are the ones infected, Robbie Williams has turned into a zombie and is chasing her and M and S is the zombie base!