How to approach a dog:
Most dogs are approachable, but obtaining the permission of the owner is a vital precaution.
At first, do not make any sudden moves, but slowly present the back of your clenched fist for the dog to sniff, only then - if it accepts you - you may gently rub below its ears - Dogs use smell much as we use sight to recognize friends, and this is how dogs learn who you are. It is like saying to each other say Hi! Are you a friend?