THE FIRST THINGS TO DO IF YOU FOUND A STRAY

1. Please be safe.  Fear and pain are the most common reasons for a pet to be aggressive. Seek assistance from animal control officers if needed.
    
2. Secure the pet with a slip lead, or in a crate.  Be careful about having an unfamiliar pet loose in your car while you are driving.  Keep a few slip leads and a small crate in your car for such occasions.
    
3. Immediately take any pet with visible injuries or disability a veterinarian who can assess it's health an whether it needs immediate medical attention.
    
4. Hope the pet has tags with current contact information for the owner.  If the pet has a rabies tag, call the veterinarian who supplied it for the owner’s information.  If the pet has a license, call the animal control agency who supplied it. 
    
5. If tags or collar are missing, take the pet to a local veterinary office or animal control agency to have it scanned for an identification microchip.  
    
6. If you are unable to locate an owner, you may relinquish the pet to your local animal control agency or shelter.  In California, most public shelters respect the Hayden Law that requires holding a stray pet for a minimum of 4 business days to allow an owner to reclaim it.  
    
7. If you have grown fond of the critter, you may elect foster it while trying to locate the owner.  
    
8. In this case, it is imperative that you notify local animal control agencies with a description of the pet, the location it was found, and photographs of it.  This way, if an owner looks for it at the shelter, you will be contacted.
    
9. Put up FOUND PET signs in the neighborhood where the critter was found.  
    
10. If you found a dog, take it for walks on leash in the neighborhood, and see if any passers-by recognize it.  
     
11. Be prepared to welcome a new critter into the family, it doesn't take long to fall in love!

how do you insure that the pet is being returned to the rightful owner?

There have been some situations where lost dogs were returned to someone claiming to be the owner and the well-meaning finder of the dog was not so sure that they were returning the dog to the actual owner.  
Many rescuers are already aware of these concerns, but here are a few tips that might help to ensure the dog is going back to the rightful owner and not someone trying to get a dog that isn't theirs:

1) Do have the dog scanned for a microchip at a local vet or shelter.
2) Do post only a minimal description of the dog in any Found Dog ads you place. 
3) Do post Found Dog fliers in the neighborhood the dog was Found and also check the area for any Lost Dog fliers matching the dog's description.
4) Do post Found Dog ads on Craig's List and in the newspapers, as well as fill out Found cards at each of the local shelters.  
5) Do check the shelters, newspapers, Craig's List, etc. for Lost Dog ads matching the description of the dog you've found.
6) Do ask any potential owner if they can provide a photo of their dog or vet records or adoption paperwork or anything else that would prove ownership.
7) Do let the potential owner do most of the talking and make sure they describe their lost dog in detail.  Make sure they can describe unusual features, such as an unusual marking, a different-colored eye, an all-black dog except hind left leg has two white toes, etc.
8) Do not ask leading questions.   For example, if their dog has a unique feature, let them describe it. Instead of saying, "Does your dog have a crimp in its tail?" ask if there is anything distinct about their dog's tail and let them provide the details.  
9) Do not post a photo of the found dog.  This gives way too much info to people wanting a dog that is not theirs.