Vets can tell is your pet socialized or not as soon they see him. For example, if a pet is happy to see a new person, he is socialized, if he is hiding behind the owner, he isn’t. The thing is, pets that aren’t socialized are afraid and they have more stress in life. So, you should socialize your puppy or a kitten, or any other pet from an early age in order to make his life better. In that case, he will be happier, have less stress and less problems later in his life. All animals are pre-programmed to be careful when they see a new person or other animal. They use this for their protection. When you socialize him, he doesn’t have to pay attention to this. Also, many dogs won’t be aggressive, so they will be safer.
If you want to socialize your dog or a cat, you will have to start from an early age. Puppies and kittens need to be socialized from 3 to 12 weeks of age. That window closes after 18 weeks. You can even start earlier with your kitten. When you adopt an adult dog, you cannot socialize him. You missed that opportunity. The socialization means that you must introduce a pet with new things and new people.
At the beginning of the progress, you will have to set goals. This means you must make a list of things you want to socialize your pet to. This includes: children, people, babies, other pets, crowds and even people wearing or not wearing hats. Also, take your pet to different environments. Walk him on concrete, grass, busses and streets.