I firmly believe that training begins the second you take possession of a dog. This is the time that their brains start absorbing and taking in, whether it is right or wrong.
there are three articles on this website that I feel are essential. The first is: The Nature of the Beast, Pup as a pack animal.
The second is: the top ten practices that interfere with training your dog.
The last, well to me is the most important: Obedience is a way of life, not a 15 minute drill.
I firmly believe if you follow these guidelines, that by 8 months you will have an extremely obedient dog that is 150% ready to go into formal retriever training whether by you or by a professional. Remember, amateurs have one advantage over professionals, and that is their love and bond with the dog.