I have recently reintroduced a concept I'd used successfully when I was teaching at the public school down in Yeonggwang: I give out [broken link! FIXME] play money (that I make myself) as incentive prizes to students who are doing exceptionally well in class (based on keeping track of points during class); later, I'll try to run as little "store" where they can buy some trinkets like pencils or pencil cases or the like.
I have one student in a class, his name is Huitaek. He's a little bit ADHD, maybe, and he doesn't do really well at accumulating points. He's actually really smart, but I can see he's been despairing of ever earning any of my fake money. So, being innovative, he had an idea (which I reconstructed after the fact): he sold his book (his class textbook) to his neighbor. I didn't realize at the time. But at some point I looked down, and noticed that Huitaek was sitting, bookless, happily gazing at one of my green alligator bucks that he held in his hand, while Junyeol was happily sitting with not one, but two textbooks open on his desk. Both were grinning. What had transpired was utterly transparent. (Note the image at right is out of date – it's from the screenshot I made of the Hongnong version of my alligator bucks; I have new ones that are Karma-based.)