Characters

What makes a character live on the page? The same things that make real people live.

Beliefs (philosophy, religion, politics).
Chance.
Economic status.
Education.
Emotional stability.
Energy level.
Environment.
Family background.
Fate, destiny.
Friends and enemies.
Gender and sexual preference.
Honesty or dishonesty.
Hopes and dreams.
Mental ability.
Obsessions, compulsions, fears, regrets.
Past experiences.
Physical appearance and self image.
Speech patterns.
Thoughts.

The story, plot, and perhaps your intuition, will tell you which elements to emphasize or dwell on. I'm a strong believer that character drives plot. If you know your characters inside and out, they'll tell you what to write.