A friend, and colleague, gave an amazing speech on how to control a class using behavior modification techniques. He has studied this topic intensively and well qualified to lecture on it. Alas, I am not so here are some links to places where you can get better information on the subject.
General overview
http://www.gainlifeskills.com/?page_id=585
Shaping
This is a good site that explains it well but not necessarily directly useful in our lessons.
http://www.ldonline.org/article/6030/
Positive re-enforcement
Good explanation, but best to avoid some things like; hugs, and touching in general.
http://discipline.about.com/od/increasepositivebehaviors/a/How-To-Use-Positive-Reinforcement-To-Address-Child-Behavior-Problems.htm
Classroom examples
http://www.learnalberta.ca/content/inspb1/html/6_positivereinforcement.html
More types of reinforcers and their effects
http://www.cehd.umn.edu/ceed/publications/tipsheets/preschoolbehavior/posrein.pdf
More in depth reading
Full publication on the subject.
https://books.google.co.jp/books?id=6-vnZJjtBGUC&pg=PA3&lpg=PA3…