DON'T write what you know.

Don't write what you know, that's what I'm telling you. It may go against what you've been told before: it's no secret that English teachers the width and breadth of the country say the exact opposite. I've been told in the past by many a teacher that if I wrote what I knew then my writing would be more believable and I'd have more to say.
As my creative writing teacher once said, if you only write what you know then you are drastically limiting yourself. There's only so much you will be able to write before you have to venture into the unknown but that's great! There's little that is more fun and exhilarating than those first moments of research, collecting facts and reading books by authors of the same genre. If you don't explore with your writing, you won't learn and you will find yourself stuck in a rut.
Every time that I have tried to write what I know, it has failed because the writing has sounded limited and conceited. By only writing what you know, you run the risk of treading on dangerous territory with regards to inventing characters based too heavily on people you know.
Try to be adventurous and if you think you won't be able to write something because of inexperience, do it. Research it, talk to people who are experienced and read books which deal with the topics you're interested in. In the end, it doesn't matter what you know because you can look it up and find out. What matters is how much interest you hold in the topic: the more interested you are, the more that will show through.
Go for it - write what you want to write about, be it the mating habits of snapping turtles or an in-depth guide to criminals of the 1700s.

Lydia