If writers followed the advice to ‘write what you know,’ novels would cease to exist. What would be the creative incentive? Who wants to write what they know? Not me.
A better piece of advice is to write what you hear. You might have to eavesdrop to make this work, but interesting lines will most likely jump out of normal conversation. For example, a friend once commented to me that people die at the height of their happiness.
Morbid? Maybe. Thought-provoking? You bet. Relevant to my story? Ding, ding, ding!
Listen for a phrase or a conversation that speaks to you with its honesty or a spark for a story line. You’d be surprised by how often this can add depth to your writing. And, that’s what you’re looking for. After all, most of us writers understand that to write what you know simply means to write with authenticity. So, pay attention. You’ll know it when you hear it.