Here is a great resource for owners of puppies (and all dogs). The book is called Puppy Socialization: What it is and How to do it by Marge Rogers and Eileen Anderson. It is published only an e-book. It comes with oodles of hyperlinks to videos, handouts and references. The videos are useful in illustrating some of the concepts. There are many photographs used in the book to illustrate the section on body language. I think it's worth reading even if you don't have a puppy, if you don't know much about sensitisation and habituation.