Body language

Ever seen a dog that seems docile and tame with its tail wagging, but the moment you walk within its reach it jumps and attack you? A lot of people have the misconception that when a dog wags its tail, it is being friendly and asking for affection. I was also one of the people until I had my first dog and after a lot of reading did I realized that it is not always the case. Besides its tail, there are many other signs that we can look out for to determine whether a dog is ready to attack, friendly or even fearful.

Below is a general list of behavior that I have come up with based on my observations and knowledge acquired from books. It may differ slight across the various breeds.

Relax
1. Standing or lying down
2. Either wagging its tail or lying naturally on the ground
3. Ear is relax
4. Either panting lightly or mouth closed
5. Eyes not staring at anything

Ready to attack
1. Standing tall and rigid
2. Tail rigidly up or out behind
3. Pricked up ears
4. Teeth baring
5. Look out for the line of hair that starts at the base of the neck to shoulders, it should be standing
6. Intense look, staring

Fear
1. Body lower down
2. Tail tuck between hind legs
3. Ears down
4. Might urine if very intense

Verbal ques
High pitch barking - excitement, especially when a family member returns
Low pitch barking - warning of possible threat, such as when the postman visits
Whining - complaining and wants attention
Growl - stay back

Recommended reads:
Canine Body Language: A Photographic Guide Interpreting the Native Language of the Domestic Dog
Barking: The Sound of a Language (Dogwise Training Manual)
How To Speak Dog: Mastering the Art of Dog-Human Communication