One form of identification is a collar with a name tag. This tag should include the dogs name and the owners information. If a dog gets loose while wearing it's collar with a name tag the finder can easily call the owner and arrange to get little Fido home as soon as possible. A couple tips: make sure that the information is current and make sure that the dog is always wearing it's collar.
What if the dog is not wearing the collar, the collar falls off, or the tags get pulled loose?
Pet owners now have a more permenant identification option readily available to them. The microchip. Learn more about Microchips here. If a loose pet is found by a shelter or a policeman they will check for a microchip first. If the pet has a microchip they will get the owners information from the online database and give them a call. Simple as that! If a neighbor or individual finds a stray pet they probably wont posess a scanner, but they can head to any shelter or veterinarian clinic and have the pet scanned there.
Microchips last a pet's entire lifetime so all the owner has to do is make sure they always update their registry with any new phone numbers, addresses or other contact information.