I love writing short stories. You can complete one in a matter of weeks, rather than the years it takes to finish a novel. You can try out new – often riskier – ideas (and sometimes, ironically, you can find the germ of a novel inside an idea you might otherwise never have tried). Here's my advice:
Follow a dream
My short stories often start with an image that has found its way into my head: a swimming pool in autumn ('The Incomprehensible Mortality of Karen Mack') or a young woman in a beret, going in a rowing boat to a small island somewhere near Skye ('The Girl In The Boat'). When you get a picture like this, sitting in your mind, take it as a sign that there's a story underneath it. Start writing and see what grows from the daydream. In a short story you can afford to try out ideas to their conclusion. In a novel, that way of working can mean a lot of wasted time – but in a short, you have the freedom to experiment much more. So use it. Lift the stones and see what's underneath them.
Use a strong voice
Voice is obviously important in other kinds of writing, too, but it's particularly crucial to have a strong voice in a piece of work that your reader will only be experiencing for a short time. You need to pull them in straight away. I often use first person narrators for my short stories, because the voice is naturally more immediate with this sort of narrative. But there are ways to cheat...
Try a new format
Short stories are ideal forms for carrying different kinds of writing. You could include a single diary entry, an e-mail, a shopping list – anything at all – without it seeming stranded, the way it might in a longer piece. If your storyline requires third-person narration, then this can be a neat way to bring in a first-person voice. In 'United Solutions', I used a transcript of a telephone conversation, combined with a newspaper article, and left readers to construct the story of what had really happened from those materials. Using unusual formats can also be a way to make your reader engage more actively with the narrative.
Choose your moment, or age
There's a lot of advice about how a short story should focus on a particular moment in time. These stories are definitely more straightforward to write. But don't feel barred from taking in decades if you want to. You can cover a lot of ground while staying cohesive if you remember the point of the story, the soul of it. What do you want to pinpoint, in terms of how it has grown, died, or changed over the long period? Try bringing in something from the wider world to act as background for this. In my story 'After The Reunion', I wrote about a relationship between a couple who had been reunited after several decades apart, with the backdrop of Berlin's reunification (when they met) and its 20th anniversary (when they were reunited). A short story is a microscope and a telescope. It is a window on a world, and that world can be on a scale that is vast or tiny. It's really up to you to define the parameters.
Keep your structure clean
Don't forget the importance of the basics. I think you can get away with most things in a short story, if you just make sure you're telling a story. A story needs characters, and problems, and some kind of resolution for better or worse. It's this structure of the story, rather than its scope in terms of time period, that needs to be scaled to fit a short word count. You won't have room for a cast of thirty characters, or the kinds of intricate plotting you can weave through a novel. But what you have instead is a stage for something pure and often more impactful. A short story, well written, can make its mark all the more clearly than a longer piece of work.