(This is an excerpt from a letter I recently wrote to one of my adoptive families that I thought might be a helpful "share")
Just a few reminders...
Most importantly DO NOT forget to get her final parvo/distemper vaccine before exposing her to other dogs. It should be almost time for that final shot by the time this reaches you. Then you can really start to socialize her. Socialization is very important. After that final vaccine, you can also enroll her in puppy classes if you want.
Second... remember that these first 6 month are crucial for her behavioral training. Small dogs like her can have a tendency to be especially bossy and disobedient because they are often allowed to get away with bad behavior because they're so tiny and cute. I know it's hard to discipline a tiny dog like her. But it's important for her to know that YOU are her pack leader. If you or other people are inconsistent with your training it can cause her to not understand the rules and confuse her. So if you have company, you might want inform them of your training rules or even put her away when company comes. I'd prefer her not to be put away because she needs the extra socializing from people outside your household. But if there are, for instance, small children who don't know how to make her behave and let her get too worked up, you might have no choice but to put her away. Once she's trained, interacting with strangers and other dogs will come much easier.
Don't hesitate to call if you have any concerns or need some input.