It is important to socialise your puppy from as early an age as possible. This will help reduce the possibility of them developing fearful responses to everyday situations, such as people, traffic and places. Early handling is essential. Socialisation occurs from 3 weeks of age and finishes around 12-14 weeks.
Therefore puppies purchased from a home or breeder that has ensured frequent contact and interaction with both their mother, littermates and people, are likely to be more sociable and less fearful as they develop.
Usually puppies leave the breeder at around 7-8 weeks of age to go to their new homes. At this stage it is unlikely that they have been fully vaccinated and are therefore not yet fully protected to go out safely for walks in public. A balance must be reached between socialisation with other dogs, traffic and keeping your puppy safe. It is fine for you to carry your puppy while out and about, to get them used to new sights and sounds as long as they are not put down and walked on the ground. It is also safe for puppies to be socialised with other dogs as long as you are sure the dogs have been fully vaccinated and the vaccinations are up to date.
Introduce your puppy to as many new people and situations as possible in its first 3 months of life. It is important to praise your puppy each time they meet a new situation, but at the same time, it is also very important not to reassure them if they find the situation fearful as this may reward the fearful response.