I’m not a fan of ‘rules’ for writers, in part because I don’t think writing can be taught. I think it can be molded, and shaped, and improved, I think instructors can inspire something in their students, open their eyes to possibilities and broaden their horizons with literature, but there has to be something there to start with. There needs to be a seed in order for it to flower.
There are conventions in writing, and structures or formulas that need following, but any rules on how you go about filling in those blank pages is entirely subjective. That doesn’t mean they’re all useless or should be ignored completely, they just shouldn’t be treated like a missing set of Commandments which, when followed, will turn you into a writer of virtue. ‘Thou Shalt Not Write in the Second Person.’ ‘Thou Shalt Write What Thou Knowst.’
There’s nothing you absolutely cannot do in writing. Of course, if you expect someone else to read or publish it, that’s when you start taking notes and deciding what criticism is valid and what isn’t. While you write, however, turn off the voice that says ‘Don’t do that.’ Do whatever you want, it’s your work. You just have realize that not everyone will see what you see on the page, and it’s your job to find the middle ground.
If everyone wrote what they know and only what they know, there’d be no science fiction or fantasy and half the prison population would be mystery authors. In Stephen King’s On Writing he talks about this old adage in a way that really opened my eyes: write whatever you want, as long as it’s honest. Writing what you know is a good place to start, a good foundation, but then your imagination takes over. As long as your characters feel legitimate, and behave as real people would in such a situation, then it doesn’t matter if you’ve never gone on safari to search for African leopards.
This is where exposure to other writing can come in handy too. If there’s something you want to write about, but don’t actually have any personal experience with, read about it. Explore the ways in which other writers approached the subject matter. Put a post on craigslist looking to talk to someone with the experience you lack.
Take a few risks, try something new. It might not work, but that’s something you ultimately have to decide for yourself.