well dont buy from a petstore-they are overpriced, and buy from dog mills. check your local papers, craigslist and petfinder.com is a great site.. you want to buy from a reputable breeder/owner, who have the parents on the premises and can tell you about any genetic abnormalities that may run in that line-ask lots of questions.
dont buy from someone who breeds the same female over and over and over... (if you are buying a puppy). best of luck to ya!