As soon as your puppy has had his inoculations and can be taken out, it's a good idea start to socialise him by introducing him to other people and other dogs.  An excellent way to do this is to attend a puppy socialisation class where he will meet other puppies of a similar age in a safe environment.  Your vet will probably know when and where these are held if they do not run them at the practice.  Let him say ‘hello’ gently to other dogs and you should also speak gently to him, the other dog and the other dog’s owner.  You will also probably be given information about looking after your puppy and may even be given the chance to have your puppy micro chipped at a reduced price.