I use Jelly Beans (or any other small candies will do) to reward children who are on task. Find a "fun" container to store your goodies in. I found a really groovy rabbit with sun glasses that ejects the candy like a gum ball machine. When I see that someone has followed directions well, is sitting quietly, and is ready to start the next subject I reward them with a goodie. All I have to do is stand up front and quietly point to the student and say one bean and the rest of the kids fall into line.