Communication

dogs parks and day camps
The biggest thing that separates humans from animals is language. Not communication mind you, but language. Animals have a pretty complex system of communication and the more complex the pack, the more complex and nuanced the communication. I briefly run down communication here but I want to really expound on it here. Both you and your dog will benefit if you learn his form of communication. Even if you do not have a dog, it is helpful to know what they are thinking and can even save you from harm!
Dogs communicate primarily through body language, sound and touch. 
Postures and movement convey rank, mood and intent. To understand what a dog is thinking or feeling you need to look at her entire body. If you focus on just one body part you could be missing the whole story and the results could be dangerous. 
ethology and psychology dogsLook at the dog’s head: If she is holding her head high then she is interested in her environment, what she smells, hears or sees. Confident dogs hold their heads proud and high. If her head is high and her neck is arched, then not only is she confident, but she is showing off her superior rank to other dogs. (One might compare this to high ranking humans who hold their heads high and puff their chests out.) If her head is high but her neck is cocked, then she is showing her interest and curiosity. If her head and neck are level, her body is crouched and leaning forward and her posture is stiff then she is ready to charge forward. This could be the result of a curious and playful nature, or an aggressive response. 
If her head and neck are level or level but lowered below her shoulder, her body is stiff and she is leaning backward then she is ready to escape. This dog may bite if cornered. 
If her head and neck are level or level and below her shoulders, her head is turned to the side and her cheek is turned up, then she is ready to appease. 
If her head and neck are level or level and below the shoulders and her body is curved so the head and tail are facing the same way  then she is feeling fearful and cornered. This dog may bite if approached.
If the head and nose are down, the nose is tucked towards the chest, eyes are averted, and the dog is crouching slightly, then she is displaying a lack of confidence and a show of submission to those who rank higher. 
Look at the dog’s tail: If a dog is holding the tail high, stiff and unmoving then the dog is assessing his surroundings. He is ready to take on a challenge if the mood calls for it. If the tail is high and has a stiff wag then he is displaying dominance and is ready to fight if necessary. 
If the dog is holding his tail high, wagging it stiffly and in a small arc the dog is willing to engage in friendly play if the other dog is willing to play with him. It may also be a sign of sexual interest if the dog in question has not been altered. 
If the dog is wagging his tail in a relaxed manner and in a wide arc, then he is friendly and enthusiastic. 
If the dog is holding his tail stiff, straight, and horizontal then the dog is assessing the situation, is interested in his surroundings and is ready to engage in chase if the individual he is focused on flees. 
If the tail is horizontal and still then the dog is interested but not really going to chase or move towards other animals or people. 
If the tail is horizontal but the tip is drooping then the dog is assessing the situation, but is unsure of whether to proceed or run. 
If the tail is down, but has a gentle wag to it, then the dog is friendly, but shy or unconfident. 
If the tail is tucked but wagging, then the dog is unconfident, but willing to be petted only if you approach him slowly. He may panic and run if you take things to fast.
If the tail is tucked and still then he is fearful and will run if approached and bite if cornered.
If the dog has tucked his tail, rolled over on his side or his back, (and may or may not urinate) then that dog is making himself the most submissive he can possibly be.
understanding dogs and their behavior
Look at the dog’s ears. If they are perked and facing forward  then she is interested and curious. 
If they are partially lifted facing forward then she is interested, but not enough to approach. 
If the ears are slightly back, but perked, then she is relaxed.
If the ears are lifted halfway and face the side, then she is worried, but also curious. 
If the ears are lowered, either facing the ground or backwards, then the dog is worried and wishes to escape. 
If the ears are lowered and  pinned to the sides of the head, then the dog is terrified, but may be to afraid to run. She will likely bite if approached or cornered. 
Look at the dog’s eyes. If he is staring intently,  and his gaze is hard and unwavering, then he is an overly confident dog and may be aggressive or display a predatory nature. 
If the eyes are averted, then he is submissive and possibly afraid. 
If the eyes dart back and forth from a person or animal than he is afraid or nervous. 
Look at the teeth. Dogs bare their teeth out of fear, predation, play fighting or aggression. If she is showing you a small portion of her teeth then she is warning you what she is capable of. As she becomes more threatening she will expose more teeth. Angry dogs who bare their teeth will also display deep facial folds or wrinkles. A dog who is ready to attack will display wrinkles from the tips of the mouth to well above the nose. 
Do not mistake a dog baring her teeth for what is known as a “doggy” or “canine’ grin. Some dogs will smile in a friendly way or as a greeting, Some dogs will grin when relaxed. A doggy grin is accompanied by relaxed posture and slightly closed eyes. A dog who is smiling will only show relaxed wrinkles around the mouth.
animal shelters and rescuesLook at the fur: When a dog is feeling fearful or aggressive, then he will display piloerection (His hackles along his back will be raised).  This is an evolutionary response to make him appear larger than he actually is. Many dogs who display piloerection are not angry dogs, some are anxious or nervous. Some dogs will do it when they meet other dogs and if he feels their is no threat, he will lower his hackles. 
Look at the posture. Remember what your mama always said; posture is important. If the dog is crouching or skulking near the ground then she is submissive and may be afraid. 
If she is standing tall, stiff, rises on her paws and leans forward then she is confident, curious, and excited. But she may also be aggressive or predatory. 
If she initiates a play bow (front elbows touching the ground, head down and backside up in the air) then she is playful and friendly. Often you will see a play bow preceding play and during play.
If she is on her back, showing her belly, then she is submissive or scared.