A common part of English classes in school is taking a text, and examining it to learn more about the author. An author’s writing often betrays their emotions, ways of thinking, and so on.
An important part of writing your characters is to ensure that your writing reflects not your views, but your character’s. You have to place yourself in your character’s shoes and think how they would, no matter what your viewpoint may be. Their reactions to even small events adds to their character, and can show more about them.
A simple example can be taken from Tom Clancy’s Rainbow Six. Staff Sergeant Domingo Chavez remarks that he has to go make dinner, which is met with surprise from the other men. “Nice to see you’re properly trained, Chavez.” Chavez simply replies that he’s confident with his masculinity, and since his wife is a doctor, they take turns making dinner.
The subtext is of course that cooking is supposedly a woman’s job, not a man’s. The character who passes the remark seems to hold that attitude, while Chavez seems to be unconcerned about it.
None of this, of course, betrays what Mr. Clancy himself thinks, but it does add to the character of those involved. It’s a very minor part, takes up maybe half a page at most, yet you learn more about how he thinks.
Pretty neat, I’d say.