My guy is a Dwarven Runecaster from the Skycrag Mountains, skilled in the arts of Misdirection and Research. His race, class and skills, which I just made up, go on our game's lists of those things, and his homeland goes on the map.
Right after I decide what my guy is, I decide he's not a Hill Troll or a Fairy; he's not a Sneak Thief or a Gladiator, he's never been to the Forest of Glass or the Gibbering Sea, and he knows nothing of the arts of Battlefield Control, Seduction, Undead Heraldry or Shadow Divination. But, having now added those things to our game, I can expect to bump into a Fairy Gladiator upon the Gibbering Sea, or to find myself in a situation where Battlefield Control might come in handy.
(Maybe, after we all decide what our characters are and aren't, we each go back and change one aspect of our characters to someone else's contribution.)
Either way, we play short lived characters in a persistent campaign setting. As our characters die horribly or retire happily or just go off camera for a couple of sessions, we make new ones by picking races, classes, etc. from the list. Every time someone makes a new character, they add new classes, races, locations, and skills to the list for everyone to drool over and say "ooh, I want to be one of those next time!"