I like to use MYSTERY student. With this, I pick a girl and boy student to watch for good behavior, they have idea who I pick. If this student does a good job during (line up, class work, centers, etc…) they get a point in our classroom dojo (the online FREE classroom management site another use r mentioned in this thread). The site even has a random student picker that can help u choose. You can also give out a raffle ticket for the mystery person as a way to motivate behavior you want to see.