Thousands of dogs are abandoned every year in the world. The fact that most of them are cross or mixed breed is not relieving at all, but shows how materialist society can be. A pure-breed dog is like a walking check, and before abandoning it, it is better to try and sell it somewhere. A crossbreed dog has no commercial value, and is usually abandoned just before the holidays, for it becomes annoying and inconvenient.
A dog that is neither ran over by a car nor shot by someone, ends up in a shelter, where it waits to be adopted. As imperfect this solution may be, it is better than these poor creatures marauding about the streets, ill and starving.
You found a dog! It doesn’t matte if you find a dog that seems to be abandoned, tied at the door of a diner or showing clear signs of abandonment: you cannot keep just like that, even if you think it will be better of with you. You have to denounce your finding, for if you don’t, you will be committing a misdemeanor, and not only that, but you could also be making a family very unhappy, if the dog happened to belong to someone else.
Let the police know you found a dog or take it to a shelter. If there is an owner, then it will probably go to the shelter looking for it. If the dog is identified, then the employees of the shelter will try and find its owner, and if nobody goes looking for it in a couple of days, then you will be able to take it home.
Anyway you will not be considered the owner of the dog until a period of time has passed; this period of time is different in every country.
Experience shows that an interested owner makes everything possible o find a dog within the first week of the loss, unless he or she is ill or away. If the owner appears within a period of time of 6 months approximately, you can then ask for a payment, to cover all the expenses the dog caused (food vet, etc).