What does it mean, “Write what you know”? I come from an Italian-French family. I worked in a fish market in RI for a Mormon minister fisherman. I lived in the servants quarters of the Marble House in Newport. I have worked in Hollywood for twenty years. I have a family member who is an alcoholic. Does that oft-used exhortation to writers mean that I can only write characters whose lives dovetail with mine? Wouldn't it be like saying that a doctor can only cure cancer if he first had cancer?
The expression, "Write what you know," first means, DO YOUR HOMEWORK. "Write What You Know" refers to the part of the writer's task that precedes the actual writing. On this level, editors and producers have a right to bemoan those writers who literally aren't filling their place at the table. The writer’s job is to do the research. It is to fill out a new world, or to add fresh details to a world we thought we knew so that we now see it in depth.
Research is always doable. It helps me to set a script in Newport, RI because I have already done the research by my life experience. But part of the crafting of a screenplay is to enter into new worlds through research and make them tangible for the reader/viewer. Don’t set a script in a scuba diving school near the Great Barrier Reef unless you have done your research in the kind of people who become divers, intricacies of scuba gear, diving education approaches, ways divers die, how cool the underwater thing is, Australians, and the Great Barrier Reef. So, the first sense of "Write what you know" is WRITE WHAT YOU HAVE COME TO KNOW ABOUT.
A great writer doen't write to “young adults” but to “young souls.” Not to aging Boomers, but to weathered souls. Not to children but to “baby human souls.” Speak to their fundamental condition not to their particular situation. What is it they yearn for? If you write to kids as if they are yearning mainly for the newest skinny jeans, or the latest iPod, you are dehumanizing them and they will disdain you. Rightly so. These are not truly the things for which a human soul yearns. They are the manifestation of that deeper yearning.