The format.

A good RP character format, just so you can have a good idea as to what to think up.

Name: Obvious
Age: Can be years or "cycles" or whatever, just give us a hint as to how old
Race: If human, apply things like (Caucasian, Latina, Asian, African etc.) if non-human, try making up a sub-race.
Skills: What are they good at, what aren't they good at, flaws, strengths
Role: If part of a squad or team, what do they generally do as part of that team?
Screenshot/apearance: The screenshot is not really necessary, but preferred.
Theme song(s): Again, only if you want to
Insignia, if applicable: If part of a certain army, or team
Current Location: Does not have to be wherever you are in the story
Current Status: Ditto
Biography: Try and give us some background. You can have it be a UNSC/Covie intel file, a tattered note, an interview, whatever. As long as we get something along the lines of where they came from and who they are, you're good.