My jobs and discipline follow the theme of baseball. I made a large poster of a baseball diamond with all of the positions labeled on it. (You can add coaches and umpires off to the side if you need to). Each position has a specific classroom job and I rotate jobs every one-two weeks. I separate my class into two or three groups and pick names out of a "dugout" and the students choose what job they want for the next two weeks. I learned not to let them pass on a job if the one they really want is already taken (it takes too long).