We cannot say it enough, socialising your puppy is so Important. Put the effort into it, do it well, and you will have a happy, confidant dog later. Miss your window or do it wrong and your dog could become socially awkward, fearful, and potentially aggressive. Not fun for you? Even less fun for your dog. You owe it to your puppy.
Puppy classes are usually a good first step. A lot of discoveries have been made over the last few years, and we now know a lot more about how dogs learn, behave and communicate. Some trainers still demonstrate old fashion methods of training, and classes can become difficult for the owners and genuinely frustrating for everyone involved. But find the right group and trainer, and you will learn important skills, while having a little fun.
Regardless of you attending puppy classes or not, you will still have to socialise your dog further, one class a week is not enough. Scientists say you have until your puppy's 12th week to introduce him or her to as many people, dogs, animals, noises, situations, smells, etc... as possible, although the whole first year is important too. So think size, colour, ethnicity, beards, hoover, coffee grinder, bus, tube, wear sunglasses in winter and hats in the summer, the list is long, you will be busy; but how fun showing off your puppy all over town.
At the moment your puppy is so friendly, he or she says "hi" and jumps happily on everyone, and you would probably like him or her to be a little more tamed. How could this little ball of fur ever become fearful or aggressive? Well... fast forward 1 year, and there you have it, barking at strangers as well as at your friends, unable to go for a walk off lead, or even go on holiday with you.