Dog body language:

 

How NOT To Greet a Dog
A poster showing do's and don'ts when greeting dogs

 

Signals
Signals, second version
A poster showing some common signals our dogs use to communicate

 

Doggie Language
Another poster showing common canine body language

 
Dog owners have often claimed they can read the expressions of their pets - particularly that tell-tale look when they have done something wrong. But researchers at a New York college tricked owners into thinking innocent pets had misbehaved - with the owners still claiming to see this guilty look. The study found that the expression had no relation to the dogs’ behaviour. And researchers found that pet owners’ belief that they could read their dogs’ “body language” was often entirely unfounded.
 
The changes we’ve made to dogs’ physical appearance do not necessarily make it easier for dogs to communicate with one another. Ha suggests that many aggression issues stem from misuse of signals and miscommunication between dogs. Voith has a similar assessment: “Based on clinical experience, but not tested systematically, dogs that are fuzzy or black are often attacked by other dogs. I think that is because their social signals are not easily detectable — if at all. Subsequent to being attacked, black or fuzzy dogs become defensively aggressive towards other dogs, generally on leash... For Herman, the implications are obvious. “When you dock tails, it takes away part of their communication signal. It’s the dog version of Botox. Ear cropping falls in the same category. Dobermans with cropped ears ostensibly look alert to other dogs. They can’t be read [accurately] because they can’t change.” It’s difficult to derive cues and information from cropped ears. If anything, their constantly alert position could mislead other dogs... It can be helpful for pet dog owners to recognize that what dogs have or do not have at their disposal could add confusion to dog-dog communication. This appreciation could help owners empathize with their dog, instead of blaming their dog or feeling angry for the dog’s behavior.