To help me get to know my (main) characters better, I use this "sketch/profile."
What is the character's...
* physical presence? (height, weight, hair color, skin color, eye color, etc...)
* personality? (get as detailed as possible - even could take a Briggs-Meyers test AS your character, to get to know him/her better)
* special quirks, phobias?
* background? (including childhood, siblings, friends, education, etc.)
* current career? (Why did he/she choose that career? How does it fit his/her personality? Is he/she happy in it?)
* family situation? (married/single? current and past relationships with parents and siblings - birth order, dynamics between siblings, parental issues, etc.)
* past loves (who were they, how did they meet, what was the relationship, how deep was it, and how far did it go, and when and how did it end?)
* How does the character react to: fear, love, death, decision-making, hard-to-like people, boredom, conflicts, crises, children, etc...
* What’s in the purse/wallet?
* What kind of car does he/she drive and how old is it?
* What’s his/her idea of a perfect evening? Perfect day?
* Neat freaks or sloppy?
* Favorite tv shows, music, movies?
* Dog or cat person?
* Religious or political affiliation?
* Any tattoos or piercings? If so, where are they located and what's the significance?
* Speak more than one language?
* How many other cities/countries has the character visited?
* Describe his/her room or living space - what’s in it? Color scheme, items (computer, clock, CD’s, furniture)? What could you tell about this character by just walking into his/her house or office?
Certainly, the list could go on and on. And the odd thing is, you probably won't end up revealing even HALF of these specific details inside your story/novel. There's not room to do that (without wasting valuable plot time), and it's really not necessary. These details are for you, the writer, more than for the reader.
I'm sure many of you already have some sort of "character sketch" you usually follow, probably even similar to this one. I'd love to hear some of the questions you use to get to know your own characters!