Have you heard of the B.U.G. incentive system? B.U.G. stands for Being Unusually Good. I'm not sure who originally thought of the idea, but it's been around for quite awhile. Students earn a B.U.G. when their teacher catches them being unusually good. Students can't ask for a bug and they can't point out to their teacher when they are being "buggy".
When I introduce this system, I like to add a little math to the lesson. I have a volunteer put 3 red unifix cubes and 10 blue unifix cubes in a brown paper bag. I explain that blue cubes represent non-buggy behavior. Students then give me examples of this type of behavior. Then I tell them that the red unifix cubes represent buggy behavior. One at a time, I have a few volunteers draw a cube out of the bag. Another volunteer keeps track with tally marks on chart tablet paper, showing how many blue cubes and how many red cubes were drawn out of the bag. I ask them if you have more blue than red cubes, which one has the greater chance of being pulled from the bag? Then we reverse the number of cubes, 3 blue and 10 red. They eventually see they will have a greater chance of earning a bug when they follow the classroom rules.
Here's a B.U.G. packet freebie for you:
These frog are part of the system, too. Students who are physically aggressive, lie, cheat, or steal get a frog. What do frogs do? They eat ALL THE BUGS!