It's no small task to create characters that live and breathe on the page, that don't hamstring your story by behaving in a way that seems implausible. You can spend weeks dreaming up the physical details of your characters, mentally filling her closet and his iPod playlist only to discover you don't really know your characters, especially what they want, and more importantly, why.
What motivates a person, makes him choose this action and not that one, makes her invest in a relationship in a particular way--this is the deep stuff of characterization. I've found that simply observing people going about their business of living is not enough to train me to understand character motivation. And because motivation is the building block of solid plotting, it's essential to get motivation right.
All this is to say that I highly recommend every writer spend some time reading in the social sciences, especially psychology, child development and sociology. My characterization in Bring to Light would not have gotten off the ground had I not read heavily and talked to experts about the grieving process and grief therapy.
In coming posts, I'll highlight some of the social science reading I've found particularly helpful.