Wow, there's a whole new batch of puppies out there and time again for a couple of reminders. It may sound a bit repetitive but the first several weeks of your puppies time with your are during a critical developmental period that you can never get back. Now is the time to SOCIALIZE, SOCIALIZE, SOCIALIZE!
Perhaps your breeder (and maybe even your vet) said, "Don't bring the puppy to dog parks, or don't let the puppy play with other dogs until they've had all their shots!" and they are right to be concerned about disease transmission. I agree, bringing the puppy to the dog park is not a great idea BUT socializing your dog with a small group of other puppies of similar age who are up to date with their shots is critical for development of proper bite inhibition as well as developing doggy social skills. Without the proper socialization dogs can and often do become dog/dog reactive, you know the ones that you walk past with your dog on leash and they lunge and bark and you think, 'my that dog is aggressive, I can't imagine why they'd have that dog out in public'. The sad reality is that dog is probably a wonderful dog who just never got properly socialized as a puppy. This is especially true for small breed dogs, because they are so small as little puppies people tend to be over protective of them particularly around larger breed dogs. Rather than protecting their dogs they end up creating a dog that worries about being around all other dogs!
Socialization should not stop with puppy play dates! It means getting your dog out and about to see and interact with all the different people, places and things that they will see in their lifetime while they are open to it! So take your puppy with you when you go pick the kids up at camp, let them meet all the kids and their parents. Take them to the soccer field, the playground, the swimming hole, down town area, any where they are likely to go as adult dogs. These trips SHOULD NOT be Bataan Death Marches, but short enjoyable outings to see new things and experience new people and places. If your puppy is on the shy side, respect that, don't force the dog closer than they are comfortable to any new stimuli, and of course ALWAYS bring yummy treats with you and REWARD your dog for being brave! Even a brave puppy can get startled by a fire engine siren, so back away and reward the puppy for bravely enduring the noise! If your puppy will not take a food treat, it may be too scared, so move further away from the stimulus and try rewarding him again!
Above all make these socialization trips fun, fun, fun. Play games with your puppy where ever you go. Let him investigate things at his own pace and reward him for every good thing he does (like sitting politely while being pet by a stranger!).