Canine communication is quite different from human communication. Humans are verbal, use frontal greetings and eye contact to communicate. Canines, on the other hand, rely on body language for communication, prefer side-to-side greetings and usually avoid eye contact.
Greeting Behavior
Dogs do not like face-to-face greetings. When dogs greet without leashes, they often make a wide circle to the side and approach the dog along the side of his body first. If this goes well, they may proceed to sniffing faces.
Friendly dogs communicate this by remaining wiggly and often lower to the ground. They will have their ears and face relaxed, and their tail low, making wide, circular wags.
A dog who is uncertain about greeting may have his tail tucked between his legs and keep very low. His ears will usually be back, and his eyes wide.
An aggressive dog will lean forward with his ears perked up and his body stiff. He may still wag his tail, but his tail will be high and wagging slowly and stiffly. If your dog looks like this, it's not a good idea to let him greet.
Many times, dogs work out confrontations with body cues. For example, if two dogs have high, stiff tails, one might lower his tail to defer to the other dog.
Dogs also communicate by scent, so many times, instead of saying hello, both dogs will urinate and then go sniff the other's urine. If that goes well, then they will greet. If your dog wants to do this, don't discourage it.
Play Behavior
When dogs play, they often look like they are fighting. That's because animal play usually mimics fighting behavior that they may need for survival.
However, dogs have pretty clear signals to indicate that they're only playing. The most well-known is the "play bow," where a dog drops his front half to the ground while leaving his back half in the air. This indicates to the other dog that the rough behavior that follows is not meant as a fight but as play.
In healthy dog play, you should see a lot of give and take. If the play seems one-sided, hold onto the collar of the dog who seems to be winning. If the other dog runs toward him for more play, let it continue. If the other dog runs away, end the play session.
Calming Signals
Dogs also communicate calming signals to one another if one dog is nervous, aggressive or too rough during play. Calming signals include licking lips, yawning, sniffing the ground, looking away and lying down. To calm themselves after a stressful situation, dogs often shake as if they have just gotten wet.
Canine communication is very effective when done properly.