One thing about NaNoWriMo is that it doesn't exactly give us weeks and weeks to figure out who our characters are. With that in mind, here's a quick and fun characterization exercise I use in my creative writing workshops that may help you speed up the process.
First, compile an alphabetical list of quirks, traits and/or other aspects of personality (positive or negative) that best describe your character. Try to avoid words that are synonyms of each other. For the tough letters (X and Z) you can use words that contain the letters versus starting with them.
Here's one of my lists:
Arrogant, bewildering, courageous, demanding, exemplary, ferocious, gifted, hot-headed, intelligent, jealous, kind, lonely, mysterious, nitpicky, overbearing, proud, quick, rebellious, sensitive, terrifying, unyielding, volatile, wistful, eXiled, young, priZed
To get more out of the exercise, take each word from your list and describe in one sentence why that particular trait, quirk or other personality aspect applies to your character (bits of backstory are helpful here.) By the time you're finished, you should have a pretty decent character outline.