I know this because I write character-driven stories (as opposed to plot-driven stories).
You don't want the reader to just see and hear the story.
You want the reader to feel the story.
In order for the reader to feel the story, she has to care about the characters.
You can have the best darn plot in the universe. But if the reader doesn't:
- care about
So, how do you create, i.e. develop, a character?
Here are some of the best ways:
- Dialogue: The character speaks in a way that matches her personality.
- Interior monologue: The character's thoughts are revealed to the reader.
- Imperfection: Neither completely good nor completely bad (makes for a more believable, and therefore, more realistic and likable, character)
- Beats: I love beats!! I'll talk about them more on another Tuesday. But for now: beats are actions sprinkled throughout dialogue. Make those actions unique to that character to help develop character.
- Show, don't tell: Show as much as possible about the character (their traits and feelings), rather than telling.
- Relationships to other characters.
- Treat them like humans: Humans disagree, forget, stammer, stop in the middle of sentences, change their minds, make mistakes, etc.
But, let the reader get to know your characters the way you get to know real people - a little at a time. You don't need to dump the whole character out right away.