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…