1. Pet Shop
2. Puppy Mill
Beware of buying a pup or dog in a puppy mill. It is only interested in making money. They don't care what happen to their dog or pup. They will just put the dog in cage and will not care or give any attention to the pup or dog.
A reputable breeder is a good choice to buy your pup. Just ask some question to them and they are willing to help you if "Not" then treat the breeder as a bad breeder who doesn't care for the pup he/she release.
A good breeder have dogs that was trained and friendly to other people.
The dog might end up in a cage but most of the time they roam around.
The pup you will buy from them will have the instinct of a dog or pack