It will be important for puppies to be exposed to all the types of people, sounds, flooring, animals, etc. that they will encounter as an adult. Doing so ensures that the puppy has associated positive experiences with all and thus is going to be friendlier and more stable. That is not to say that they will not be wary of strangers and alert you to such while on their home property. But dogs that leap on other dogs or people are not "just saying hello" they are unruly jerks. Thus my program for socialization is summarized below. This is a program I have compiled from subject matter experts and is not proprietary. I have utilized information from well known trainers like Karen Pryor and Puppy Culture. But there are also numerous trainers that are not famous and offer important insights you can't get from a book.
The puppy area will contain a rotating array of items and include an indoor area and outside area. Sounds will be presented as an audio CD first to identify puppies that have natural sound aversion, and then I will desensitize before exposure to actual noise making item (not CD) which includes the accompanying percussive sound waves. This takes time. This takes effort. This makes a better dog.
Gapped wood slats
Chain link fencing (horizontal)
Child under 10 years
Groups of 4+
People wearing costumes, sunglasses, hats, heavy coats, and holding packages
Battery operated toys
Chain link fencing