The worlds a big place so here are some tips and links which may help you..
Locating a reputable breeder can be a feat in itself, anyone can easily say they are reputable, as knowbody wants to think of themselves as being disreputable! We are probabley the largest kennels in New Zealand, yet we breed a fraction of the dogs compared with others with a lot less breeding dogs. Check out how often a bitch has had a litter, a puppy farmer will breed as many litters as possible out of their bitch which in our opinion is not right. The New Zealand Kennel Club will have the breeding records for each dog registered with them if you have concerns.
Over 35 years ago we had problems trying to find a reputable breeder. When choosing a breeder we suggest you do your homework, and do not rush into things. My wife (Sue) and I spent 2 years looking and learning all we could about the rottweiler prior to buying our first dog. Below is a photo taken of my wife as a teenager with our first dog, he was well bred coming from respected Uk champion producing kennels Abukadra and Rottsann lines.
Max was not the best of show dogs, but we learnt a lot from him.
Locating a reputable breeder
Don't just accept buying a pup from an advert, do your homework!
If you care about the breed then Don't buy from Trade Me, contact the NZKC, or ask for recommendations
Dont accept everything you read on the web, ask other owners
You should consider visiting a breeder, and make up your own mind
This can be very effective way of finding a good breeder, because only those that are happy with a breeder will recommend them to someone else! This person will have been tried and tested, and found to provide a good quality pup and service.
Breed Club Secretaries
They are a good source of obtaining information of quality reputable breeders, these breeders would be expected to follow the breed club guidlines when breeding a litter.