ATTENTION: Never approach a lost dog like you approach to your own canine. Be careful, and make sure to be very gentle when approaching to a lost dog. They might feel terrified and you might look like a threat to them. If you don’t have an experience whatsoever with strange dogs, then the best thing to do is to contact an animal shelter. They can take further actions to help the lost dog. If you have experience then make sure to follow these 8 steps if you ever find a puppy wandering around the streets.
1- Approach carefully
Be kind and gentle, and let them know that you want to help. 
