I love this video technique by 7th degree BJJ BB Marcus Soares (http://www.marcussoares.com [2]). In Brazil he if referred to as the Encyclopedia of Jiu-jitsu for his knowledge
Here he demonstrates how to defend the back attack and reverse and apply a submission
See video here
http://www.youtube.com/watch?v=EJkfp3EpVoA [3]