Come up with a story by coming up with the setting first. Let the characters follow. But make them be out of their element.
Is your character a timid girl who wants to be a librarian? Find a reason for her in a place with a lot of people. Make her do a speech/performance/competition.
Is your character a brash young man who wants to be a wrestler? Put him in the military, where he must learn discipline.
(I know that I put the characters first in these examples, but what I mean for you to do is to create a place with, say, a lot of people in it. Then find a reason for a character who is out of his or her element to be there. And build your story around that.)