One of the things I've done is to interview my characters. I write about twelve questions ranging from, "What would you say is your most annoying habit?" to "What motivates you to get up in the morning?" There's really no template or requirements to the questions; the goal is to gain insight into just who your characters are as people.
Once you've interviewed all of your major characters, go back and retread your interviews as if you were actually asking the questions to another person. Maybe have someone else read the answers you came up with. You'll be surprised how effective this is.
Until next time, keep those keyboards warm.