In my opinion, the best place to buy your puppy is from a reputable hobby breeder. How do you find one and what makes them reputable? The best place to start is www.akc.org On the American Kennel Club’s home page, click on “Dog Owners”, then “Breeds”. Each breed will have a link to what is called its “parent club”. The parent club’s website usually has a breeder referral list on it where you can find breeders that are showing their dogs (in the breed ring, or agility or obedience, hunting/working trials etc…) and most likely have signed their club’s Code of Ethics.
Generally the breeders you find on parent club breeder referral lists know and understand the health issues of their breed and test for those issues, breeding only clear stock. If you want a Boston Terrier or a Labrador–go for it! Look for a reputable breeder who asks you MANY questions and will be a resource for the life of your dog. Don’t be afraid to look for the breed you want–you can find one through the American Kennel Club’s site.