Just as with "less is more" the old chestnut "write what you know" is not in and of itself bad advice. But when we reduce these old adages to bumper sticker slogans without thinking about them, we often end up needlessly limiting ourselves as writers. In a world where lawyers and reporters and ex-military guys are writing thrillers in which the protagonists are lawyers and reporters and ex-military guys, new writers often maybe feel it is their destiny to mine their own lives for the bits and pieces they will cobble together for a work of fiction. Good. You should. It's a rich mine. But it's also a dark hole, and you don't want to get stuck down there.
Don't misunderstand. If you have experience in a combat zone in Afghanistan, then you probably have some great material at your fingertips. Hi-powered litigators probably have some cool stories to tell. But if Gischler were to "write what he knows" you would soon be the victim of a novel about a comic book writer sitting in front of his computer all day who may or may not be in his boxer shorts, sipping his 4th cup of coffee who then watches his wife play Sykrim on the X-Box in the evening after his 8 year old son goes to bed. This novel would be described as the exact opposite of riveting.
Writers too often reduce this advice to simplistic thinking along the lines of "I've never been to Mongolia, so I can't set my novel there." Bullshit. Anthony Neil's Smiths great novel ALL THE YOUNG WARRIORS is partially set in Somalia. He's never set foot in the place, but it reads as authentic as anything.
And Smith's novel is also partially set in Minnesota where he lives and works. That's because Smith knows "write what you know" is a tool ... not a fallback position. He used what he knows for part of the setting of his novel but didn't let himself be limited. Writers cannot allow themselves to be trapped in their own back yards.
Part of the way to tackle the problem is simply to KNOW MORE. It should be part of every writer's mission statement to fling themselves out into the world and soak up as much of it as possible. Trust me, these experiences will find a way sooner or later back into your fiction.
And lastly, "write what you know" comes down to attitude. In a student's work, I can often tell when they are faking it. Hear this: IT IS OKAY TO FAKE IT ... AS LONG AS YOU DON'T GET CAUGHT. And when you start faking it in a half-hearted way, if you haven't done your research, if your tentative and apologetic, it will show. Every time. But your best bet is not having to fake it. Tap into yourself. If you know what it's like to feel joy or loss or terror, then grab those feelings with both hands and drag them to your characters. Knowing YOURSELF is the best way to "write what you know."
If you've been telling yourself "write what you know" keep in mind it's NOT bad advice. Not really. But it's not necessarily bad to write what you DON'T know either. "Write what you know" should never be an excuse to cop out of exploring, innovating and discovering.
I mean, how hard is a Google search? It's a start. Educate yourself. Put one big toe outside that comfort zone.