There's no real set criteria for getting a quest form. Several people have gotten minor quest forms just for living long lives, being consistent in their RP, and sticking with their character/role even in the worst of times. They are meant to be a reward for people who can make a solid contribution to the game in ways that don't involve mass-murdering everybody in sight.

The people that got the really nice quest forms were usually very exceptional in one or more ways, and generally impressed several imms over a long period of time with their efforts or devotion to duty.