In order to keep current in the field of pet care continuing education is important. I recently I purchased the book "Off-Leash Dog Play A Complete Guide To Safety & Fun" by Robin Bennett and Susan Briggs. This book is imformative about dog communication, with the goal of having fun and safe playgroups. The book goes into extensive detail so I will just highlight some important information for all dog owners.
Dogs communicate with their entire bodies. Body language signals are sent through the dogs body posture, ears, tail and facial expression. Ear 's slow and small rhythmic wags they are concerned about something and on guard.
Social gestures tell the mood of a dog or show supordination like blinking, champing, freezing, looking away and pawing. Movement can also tell such as the back roll, lip licking, shoulder bump, yawning when not tired. They can also be warning signals like growling or guarding (Toy, food, etc.)
The book also talks about play behaviors and the different play styles which differ by breed. For example sporting breeds like a rougher play style while herding breeds like to run and chase. So it's important to group dogs with similar play styles together.
The book goes into detail about stress in dogs and aggression, signs to look for and how to deal with it. This is useful information for all dog owners who wish to socialize their dogs and very helpful for me to lead playgroups.