Before Script Frenzy started, I prepared character dossiers for my characters using this chart:

http://www.epiguide.com/ep101/writing/charchart.html

It's a really helpful 5 page questionaire that asks you to fill out everything about your character, down to their favorite foods and distinguishing scars.

I just printed it out, wrote the first things that came into my head when I thought about my character. Then I saved the dossiers until the Frenzy started a few days later.

The questionaire really helped me flesh out a lot of character details before the Frenzy, so when I was writing the first draft of my script and got stuck, i'd refer to the questionaire if I needed to remember certain things like what my character would order at a diner when talking to another character. Even one small detail (the most prized possession of the main character's love interest) helped me insert a vital and very much-needed subplot!