What does it mean to “write what you know”? Based on some of the submissions I receive, I fear many writers are taking this common piece of writing advice too literally.
Audrey Niffenegger has never been a time traveler or a ghost. Robin McKinley has never met a vampire or a dragon. Margaret Atwood has not lived through the rise of a theocratic dictatorship or the end of human civilization. Jonathan Lethem is not an astronaut, or as far as I know the boyfriend of one. Shakespeare was never the king of any country, and his father was probably not killed by his step-father. Philip Roth did not grow up in Nazi America.
And so on and so on, and yet, they all wrote what they knew.
It’s helpful to draw upon your own experiences when you’re writing, but there's autobiography and there's autobiography. I work plenty of my own experience into my stories, but I don't get confused between myself and my characters or insist that they act the way I did or that events happen the way they happened to me, or even that the experiences I’m drawing on have any obvious relationship to the ones I’m writing about. For example, take my Alzheimer's/vampire story completely aside from the futuristic vampire backdrop which obviously isn't autobiographical, I'm also not a caregiver for somebody with Alzheimer's, nor a short order cook, and never have been. But I couldn't have written as convincingly from the point of view of a caregiver without the experiences I've had with my maternal grandparents, as well as family conversations about their deterioration and care requirements, and of course a great deal of research.
Research is what allows you to write factually about things you haven’t experienced directly, so you can put your character in 16th century China or on the moon and avoid anachronisms or scientific inaccuracy, so your readers are not pulled out of the story by knowing more than you do about its backdrop. Writing what you know, on the other hand, allows you to give the story emotional accuracy. For example, while my facial transplantation story drew information from my day job as the administrative assistant to several head and neck surgeons, as well as a lot of research on PubMed, to make it emotionally convincing I needed to draw on my own life experiences of times I have felt socially awkward and alienated.
Think about the emotional core of your characters’ experiences, and relate them to times in your own life when you have experienced something sufficiently emotionally similar that you can relate to their joy, their pain, their fear, their whathaveyou.
If you’re having trouble with a scene or character, break down what your character experiences into its most basic emotional components, then think of a time in your own life when you have felt those emotions (even if the incident that brought them on has no relationship to what your character is going through). Say your character has just found out their husband is cheating on them; think of a time when you’ve been betrayed by somebody you trusted. Say your character is an assassin sent to kill an old flame; think of a time in your life when your duty has conflicted with your desires. Say your character is facing seemingly insurmountable odds in a battle for the future of the human race; take a time when you’ve faced something difficult and expand on those feelings.
Writing what you know provides the basis for fiction that feels true to the reader. It means mining your past (especially the weird and painful parts) and, to torture this metaphor a little, smelting your experiences into stories that shine with authenticity.