A short story can be very short or it can be a medium length, or even a novella. The problem for many writers is getting their tale into the length required, or aimed for. Some can write very short stories and struggle with the longer versions wanting to cut out what they see as padding. Others have equal difficulty writing the short versions.
For both writers the exercise of writing out of their normal fashion is useful. For the novel writer attempting short stories is a way of training themselves to write more concisely and get the best out of their writing. Obviously for the writer of short fiction the enormous task of writing a novel is daunting.
The trick for the latter is to treat each chapter as a short story with a similar theme and the same range of characters. The short fiction is much like writing for a soap opera, you have to begin, write a middle and leave the tale hanging to use it for a novel, or conclude the tale.
The skill is in writing to a set formula and ignoring the fact.
The challenge for most of us is to allow our creativity to be controlled by discipline but writing is a discipline and any extra skill that enhances your prose is a good move.
Some comments on writing short stories are, in the main, that it is useful to concentrate your story structure, to create a discipline that is useful for longer prose in that it tends to restrict you to getting to the point quickly. The last is a great tool for packing more into your longer stories and will help when cutting out the ‘purple prose’ so beloved of the long winded descriptive writer.
To paraphrase, a short story such as ‘The last man on Earth turned in surprise when he heard a knock on his door.’ carries everything a short story needs including an ending that leaves the reader with a mystery. Whether or not it has a beginning, a middle and an end is a moot point, but it has a protagonist and an unknown antagonist and leaves the reader wanting to learn more. The object of the tale is to let the reader engage with the story and anticipate an end, or project an ending although the ending is the knock on the door.
The idea is to entertain and allow your reader to interpret the tale in their own way but to also direct them where you want them to go.
Sometimes the short story is a glimpse into a passage of a larger tale, or is related to a longer piece of fiction. Others are deliberately complete tales that make up a series, and we are all familiar with the Sherlock Holmes tales that use the same characters in each tale as protagonists that give consistency to our expectations.
The skill comes in creating a tale that is unpredictable as to the conclusion and satisfying in the telling. Most of us have trouble with that and that is where our peers come in handy when we read them out loud and receive constructive criticism. The satisfaction is having the faults pointed out and the good bits praised.