Dashiell Hammett wasn’t the world’s greatest writer. But he had something vitally important: credentials. He’d been a professional private eye for the San Francisco Pinkerton Agency for years when he began writing his ground-breaking, gritty, realistic PI mysteries set in—you guessed it—San Francisco.

Ivy Compton-Burnett was told real families don’t act the way they do in her fiction: secretive, back-stabbing, prone to multiple marriages and bare-faced lies and theft and suicide and even murder by neglect. “Oh, but they do,” she said. She was herself one of the eldest of an enormous mixed family full of malice and intrigue. Her twin youngest sisters committed double-suicide in their locked bedroom on Christmas Day, while the rest of the family was home, and are now suspected of having been lovers.

Stephen King uses a medical expert.

What does this tell us?

KNOW YOUR SUBJECT. If at all possible, have professional experience in it. Failing that, find an expert who does. Interview (that’s right—even for fiction). Do the research. Read the books, watch the documentaries, study the reference material.

When an agent reads an author bio that says, “I don’t have any experience in this field, but I can picture it,” I’m afraid that’s a donation to the circular file right there. However, when they read one that says, “I’m a retiring homicide detective with the Chicago PD,” for a mystery about an unsolved series of murders in Chicago’s notorious Englewood neighborhood or, “I’ve been the head of ER at the Las Vegas Valley Hospital for eight years,” for a novel about a recovering gambler turned doctor who gets embroiled in a local casino scam that implicates the head of a fictional Las Vegas ER or, “I spent two years interviewing young streetwalkers in the red-light districts of San Francisco, Seattle, Portland, and LA,” for a white slavery horror novel set in the underworld of West Coast prostitution. . .then they’re going to sit up and take notice.

Even Compton-Burnett, who wrote literary novels entirely based on inner-familial warfare, could have said, “After sixty years as the matriarchal eldest sister of a mixed Victorian family of twelve, four of whom died young and all of whom bear intense hostility toward certain others, I have accumulated a certain knowledge of human nature within the confines of the traditional Victorian family milieu.”

Of course, the quality of her writing also helped.

And for those who never get enough, Chuck Sambuchino has a whole post of author bio do’s and don’t’s.