Warrior Poet
Explorer
There's always the cinematic way, which I've used from time to time. Look to a favorite movie that gathers together a group of strangers to accomplish a task.
For example, Seven Samurai or The Magnificent Seven. Before the first game, talk to one of the players and find out if they'd be willing to undertake a task, perhaps for coin, perhaps for personal glory, perhaps for charity. Then simply make the task something more than one character can tackle. Time to find some other samurai to defend the village ... time to find someone to help bury that body on Boot Hill that no one is willing to transport. Then challenge them with something that forces them to work together and come to appreciate each other in a fight, in solving a riddle, whatever.
Another possibility: gather them all (as strangers) in a tavern, i.e. they just happen to all be at the same place. A group of bounty hunters burst through the door and point each of them out, calling them by names that aren't theirs, and saying they are wanted. Clearly, there's been a case of mistaken identity, but the bounty hunters don't know that, and it's hard to reason with someone who's trying to gut you with a short sword. As mundane bar patrons scatter for the exits, the fight is joined, and suddenly the party of strangers is united in common plight. If they survive the struggle, well, there's already a mystery waiting for them: who set the bounty hunters after us, and why? And who the heck are you guys?
Warrior Poet
For example, Seven Samurai or The Magnificent Seven. Before the first game, talk to one of the players and find out if they'd be willing to undertake a task, perhaps for coin, perhaps for personal glory, perhaps for charity. Then simply make the task something more than one character can tackle. Time to find some other samurai to defend the village ... time to find someone to help bury that body on Boot Hill that no one is willing to transport. Then challenge them with something that forces them to work together and come to appreciate each other in a fight, in solving a riddle, whatever.
Another possibility: gather them all (as strangers) in a tavern, i.e. they just happen to all be at the same place. A group of bounty hunters burst through the door and point each of them out, calling them by names that aren't theirs, and saying they are wanted. Clearly, there's been a case of mistaken identity, but the bounty hunters don't know that, and it's hard to reason with someone who's trying to gut you with a short sword. As mundane bar patrons scatter for the exits, the fight is joined, and suddenly the party of strangers is united in common plight. If they survive the struggle, well, there's already a mystery waiting for them: who set the bounty hunters after us, and why? And who the heck are you guys?
Warrior Poet