Um, hrm. Hrm, hmm, hmm. That's a good question. Short answer is that I want to be very sparing in what I reveal about my characters because their backstories and even names would spoil the plot, and I'd feel terrible if your bio was long and detailed and comprehensive and there's mine like

character name: ???
character age: ???
character bio: ???

For one of my charas, I can't even say anything about them, and then for the main one I would really only want to give a physical description (which would come in during his introduction anyways). So, uh. How are we gonna go about that? I'm stumped.

EDIT: idea. what if we have character sheets where we fill out information as it's revealed in plot?