It's one of the burning questions most new dog owners ask, simply because in most cases the puppy has been cooped up in the house and is so obviously ready to run and play...but you still need to do what's best for the puppy and abide by the sensible rules and established guidelines.
There are so many reasons to keep your puppy at home until the right time: diseases and viruses like canine distemper and parvovirus are not merely dangerous and can in some cases prove fatal. They can survive actively in environments where an infected dog may have walked and are an ever present threat to puppies who have not been properly prepared for their first adventure.
These warnings are not intended to scare you as a new dog owner, they are here as an important guide: your puppy is still developing its reistance and immune system for the outside world and walking them when they're not ready is like walking into a room full of people with flu when you've not come into contact with anyone for a while: you're more than likely to contract it! This is why vaccinations for young puppies are not a choice - they're a complete necessity.
The standard recommendation from vetinary surgeons is two weeks (of fourteen days) following your puppy's final booster vaccination. This should coincide with the puppy reaching around sixteen weeks of age. For many people, this is the most difficult time in the life of a puppy (much in the same way that many parents struggle with the time when their children are quite obviously ready for school but still too young to go). As far as introducing your puppy to other dogs, this can be done with vaccinated dogs at around eight or nine weeks old.
Research has shown that puppies respond best to socialisation when they hit the eight to ten week mark and this period tends to extend to around sixteen weeks. During this time, pushing the boundaries of your puppy's comfort zone with new people and situations is a critical part of their self-development and can do wonders for their confidence. As mentioned above, this should only be done with dogs who are up to date with their vaccinations and are therfore 'safe' companions for your puppy to interact with. Keep in mind that this is the arguably the only opportunity to start your puppy off on the right track with regards to developing a friendly nature and a rapport with other dogs, not to mention a healthy exposure to adults and children alike.
Once your puppy has been exposed to the outside world, it is still important to keep up with vetinary health check consultations spaced no longer than six months apart.