Ask any visitor that involves visit to handle the puppy around; coming in contact with the paws and feeling among the toes; playing with the ears; providing restrained hugs; using the mouth and starting the mouth positioning your finger on the puppy's tongue. If at all possible expose your puppy to children and teach them how to handle the puppy dog properly. Always make sure when children and young dogs are playing jointly that they are supervised. You do not want the children to experience too roughly with the pup and you don't want the doggie getting so hyped up by antics of children and becomes uncontrollable.
A whole lot of puppy socialization can occur in the home environment - exposure to loud banging noises, such as clanging pans and pots, vacuum cleaners, washing machines, grass mowers, etc.
Puppy preschool or kindergarten is a superb avenue for socialization with other puppies of an identical age. However, the discord comes from the question of puppy vaccinations "could it be safe to take a puppy out during this time period?" That is a problem because on the main one palm you want to teach your pup to be sociable but keep the puppy safe at the same time.