A wagging tail means a happy dog
People say that a wagging tail means a happy dog. In fact, not all wagging is the same. A tail waving back and forth means a dog is anticipating something. A tail at mid-height, level or lower to the ground and wagging is indeed anticipating good things. A tail held straight up and slowly waving combined with a tightly closed mouth can mean “One false move and I will attack!” Stay calm but beware this one.
Remain still, keep an eye on the dog without making eye contact, and wait until the dog relaxes his body language or walks away. Then slowly remove yourself from the situation never turning your back on the dog.