Sometimes we think that with our pet living with us he has already socialized, but what we do not know is that the dog must be used to dealing with other dogs and even with other animals and people different from his family to learn to behave. It is the socialization, and should be done especially during the puppy stage.
Socialization helps them learn from other dogs how to communicate and respect yourself, how to play and also gives them more security when meeting new friends. A dog that has socialized well and has become accustomed to all kinds of people, dogs and other animals will have no problem and will know how to recognize the signs that will make him withdraw or become friends with a good companion.
It is a big mistake that many owners make that separate the puppy from other dogs. While you do not have all the vaccinations, we can take you home to friends or family who have their dogs vaccinated, because the environment is safe. In this way they can get to know other dogs. If they are their age they will learn to play and treat their peers like that, and if they are older they will learn about the behaviors of adult dogs, which also tend to put a brake on their playing behaviors when they lead to aggressiveness.
On the other hand, it is essential that the dog know how to deal with other people, with children, seniors and adults, and meet people without being afraid. A balanced puppy will be willing to meet more people and will be curious. In this sense, we must also educate children to approach them and introduce themselves, so that they feel mutual respect.
All of this must be done in the puppy stage. With adopted dogs, there may not have been time, and the work will be greater in case they have acquired bad habits, but the good thing is that dogs are very intelligent and learn quickly.