I did this for a game of Cold City, but I think it'd work for any game where the characters have shifting agendas or motivations, and where revealing those in play is part of the fun.
I wrote four characters, each with a different national background and a different draw into the situation. By themselves, the characters were fairly stereotyped, straightforward archetypes. An American ex-diplomat, a Russian former soldier, a French Resistance fighter, and a German Bureaucrat.
I also wrote up four "secret agendas", representing a mission given to the character by the spy agency they work for, organisations like the CIA, Gehlen Org, and so on. Here's an example one:
CIAAs well as the secret agendas, I wrote "personal motivations", individual motives for the characters, these were also randomly assigned. Here's an example:
Your Mission: There’s a Soviet mole in the RPA. Intercepted transmissions indicate that they’ve been assigned to this mission, but don’t give any clues to their identity. Find the Russian agent and eliminate them. You have a syringe of insulin which will kill someone without leaving any traces.
Answer now: How did you come to work for the CIA?
Answer during play: Are you willing to kill a colleague, and possibly a friend?
AbsolutionSo you'll notice that in those examples there's a bit that says "answer now". After the players chose their characters, I randomly handed out the secret agendas and personal motivations. The players then had to work out how these three elements fit together into a whole person.
You did something terrible during the war, something you can’t forget. Maybe this mission is your chance to redeem yourself, or maybe it’s where you finally meet your punishment.
Answer now: What terrible thing did you do?
Answer during play: What will it take for you to find absolution?
My hope was that building the character themselves, out of pre-generated pieces, the players would feel a little more ownership of the characters, and play them with a little more nuance. I've found that sometimes in convention games, players can play their characters as slavishly devoted to whatever cause or motivation they're given at the start of the game. For this game, as I think Cold City requires, I wanted the characters to have multiple conflicting goals. I think having the players work on their characters themselves helped them buy into the characters' goals, but also helped them see those goals as negotiable.
In play, it worked out pretty well. The players all reported feeling pretty connected to their character, and they enjoyed answering the questions before and during play. I was really happy with how that aspect of the game worked out.