Your characters probably read like cardboard cutouts, doing expected things in expected scenarios. The fix is deliciously mean: Deny them the things they expect! When you shove characters out of their comfort zones, they do unexpected things and grow more complex in the process. Got a cliché girly girl who jumps into her car after school and races to her room for a good cry when someone hurts her feelings? Slash her tires and force her to walk home—in the rain no less . . . and then make sure no one’s home to let her in. How will she respond to being stuck outside after a day like that? Will she find humor in Murphy’s Law, or will she bash her way through a window? Either way, we’ll get a look at her mettle. She won’t be a cardboard cutout just going through the motions. She’ll be going through the emotions—and deepening as a result.