One of the first things aspiring writers are told is: Write what you know. And if you’re going to write about something, learn all you can about it so you will be able to “write what you know.” Many novelists set their stories in their own stomping grounds, their home state, territory they are familiar with. Anita Shreve’s novels are based in New Hampshire, John Grisham writes about the courtroom.
The question comes, though, what of those who write in the science fiction or fantasy genres? These people write about something no one knows.
J.R.R. Tolkien (Lord of the Rings, et al) drew maps and pictures of the lands of Middle Earth, the Cracks of Doom and Shire. By the time he wrote his novels, he knew the land he had invented as well as I know North Texas.
Ann Rice (Interview With A Vampire) tells that when she wrote this novel, based in her home city of New Orleans, she was experiencing spiritual battles. She told a television interviewer that during that time she felt very much like someone from another world trying to find her way. She knew the feelings a vampire might have and she wrote those feelings. After she returned to her Catholic faith, she studied the life of Jesus with intensity. She has since written two novels about the life of Jesus, Christ the Lord: Out of Egypt and Christ the Lord: The Road to Cana.
So, writers out there, write what you know. You know a lot more than you think you do. Take your feelings and experiences and give them to your character.