Here's the common signs of aggression (and non-aggression): Growling, snarling, and baring teeth are obvious displays of aggression and should be treated as such.An angry dog may show the whites of his eyes, especially if these aren't normally visible. Pulled-back ears laying flat against the head are a telltale sign of aggression, whereas normal floppy or elevated ears usually signal a dog's nonchalance. If the dog approaches you with its body relaxed and with a sloping curve in its midsection, the dog is probably not going to attack. A dog whose body is tenses, straight and stiff (head, shoulders and hips aligned), on the other hand, means business. A loping gait means the dog is playful and checking you out. An even, steady run means the dog may be dangerous.
Assume all unknown dogs are threats until proven otherwise. In general, the best policy when it comes to dog attacks is to do everything you can to avoid them in the first place. If you see a dog that may be dangerous, stay away. Report any dangerous-looking dogs or possible strays in your neighborhood to the authorities. Teach your children never to approach unfamiliar dogs until they are sure they are safe. By giving all unknown dogs a wide berth until you find evidence that they are safe, you can avoid the majority of dangerous dog encounters.