What I did:
1. Pick a name. Know that a name gives a sense of personality right off. "Mildred" gives you a vastly different image than "Katie" does.
2. 15 things. (See below)
3. Police Rap sheet. If your character would go missing, do you have enough details that the police could track them down? (Consider a list of things to ask, like eyes: shape/color/glasses/ect, clothing, where they might go, etc)
15 Things About Your Character:
5 Things Your Character Fears (in order from least afraid to most)
4 Things Your Character Loves Dearly (in order from least love to most)
3 Things Your Character Is Embarrassed About (in order from least embarrassing to most)
2 Things Your Character is Proud of (least proud of to most)
1 Thing They'd be Willing to Kill or Die for (state whether they'd kill or die for it)
Hope it helps!