1. Don't write what you know about; write what you care about, because if you don't care, why should anyone else?
2. We live in the age of Google and Wikipedia--anything you don't know, you can research. Do the research, then let your imagination fill in the blanks.
3. Write what you enjoy reading, because if you enjoy reading it, you should enjoy (to some degree) writing it, and this will show up in your storytelling, making it more likely readers will connect with you.
4. No author is universally loved. Find the people who love you and write for them.
(And always) Be Brilliant!