What is his or her darkest secret? What secret would they protect against at all costs?
If you’re writing a children’s story, obviously the secret will be different than if you’re writing an adult’s story.
Stop. Don’t choose the first one that comes to mind. Come up with four or five secrets. Which fits your character best? Maybe they’re all secrets for this character, but perhaps only one or two are.
I recently read a story in which the main female protagonist is a kindergarten teacher who was having an affair with a 16-year-old student at her school. You’d think that was her biggest secret. Nope. It would be a toss-up between murdering her family’s housekeeper when she was 10 (by shutting her in a burning outbuilding) or possibly murdering her college boyfriend – also by fire. And then she goes and kills her husband – and doesn’t really bother keeping it a secret. (I won’t be recommending this book, folks.) Or maybe her biggest secret is that she’s slowly going crazy. Just like her mother did.
What happens when someone finds out? Someone he or she didn’t want to know? How do people react? What happens to her? What happens to the person who found out? Does your character try to cover his or her tracks?
Come up with four or five different ways people could find out. And think about what happens next for each one.
Knowing your character is hiding something can uncover a truth about them that you never would have known before. And it doesn’t have to be something sinister. Your character’s darkest secret could be that she snuck out of the house one night to T.P. someone’s house with a friend.