It is important to take action if you find a stray dog, as it could be injured or cause a traffic accident if left alone to run loose on the roads. A stray dog should be reported to the local authorities and also to the police to ensure that the matter is dealt with properly. Take note of the type of dog it is, where you saw the dog, if you could keep hold of the dog and take it into a safe environment, and where it can be collected from.
If the dog is friendly, you may want to keep the dog in your home as it would seem like a good deed to do. Of course, many dogs are abandoned by irresponsible owners and you may feel like you can give the dog a better home. However, the stray dog should still be reported to the relevant people in order to allow them to attempt to find the real owners who may have genuinely lost their dog. Alternatively, the owners may be known to the local dog warden who may have cautioned them before about letting their dog run loose and they can take the appropriate action. Additionally, if a dog has been living on the street for some time, they may have contracted an illness or have developed some behaviours that are not immediately apparent.
A dog that has been checked over by an animal rescue shelter may be safer to take into your home.