I give out stamps. 6 stamps=1 piece of candy. They have to come see me during lunch time to get their candy. I do not give it out during class because it is a huge distraction.
I use stamps because I don't like to waste paper, ink, and time with the coupons. In my opinion, the stamps are just easier. The first day of class, I give them a stamp grid and have them glue it in their notebooks.
I have been here for about 4 months, and when I first arrived, I did not give any reward for volunteering, good behavior, winning games...
But I decided to give it a try this school year, and it has worked wonders. I could never get students to volunteer, even the students who spoke almost fluent English. The first day I gave out stamps for students who would introduce their partner, and I had whole classes volunteering, even the boys! It was pretty incredible. We will see if their enthusiasm lasts!