kymbo - the need for a third vaccination for your puppy will depend on the brand of vaccine it was given at 12 weeks. There is at least one C5 vaccination on the market that has a 12 week claim. This is good from a socialisation point of view because technically your pup is fully vaccinated and safe to take into social situations from 7-10 days after it's 12 week vaccine. Just remember that the vaccines aren't 100% and a young puppy's immune system is not fully matured, so still avoid high risk areas where parvo could still be an issue.
I think it's important for pup owners to find a compromise that they are comfortable with when it comes to whether to wait until their dog is fully vaccinated to begin socialisation. With socialisation being so important you should definitely be exposing your pup to different environments/people/places/everything else from the earliest age possible. But remember that this can involve taking your dogs on car trips, making loud noises in the house (cd's with fireworks, thunfer and loud noises on it are brilliant and a lot of vets sell them), and having lots of people come over to visit your pup (and help with training!!). If you want to walk your pup outside your yard before it's fully vaccinated my general advise would be to stick to the footpath (pup walking on the concrete, not nature strip) or in low risk areas where there are less dogs. If you really want dog-dog interaction then look into puppy pre-schools (which I highly recommend for any puppy!!!) where the requirement is usually that the pups have at least their first vaccination.
Oh, one other thing, you should avoid vigorous and energetic activities in growing puppies. I know that many puppies are super energetic and seem to just want to run and jump... but too much excercise can over-stress and damage their soft growing bones, ligaments and joints. This is more important in larger breeds, especially those prone to hip/leg/joint problems later in life, like rotti's and labs.
