Anyone can find a bargain priced dog from the money-hungry backyard breeders. The trick to buying a dog is to find one out of good stock where much planning and effort was made to produce the finest animals possible. These animals are not cheap. Money was spent to obtain the best breeding stock that would produce with consistency healthy, both mentally and physically, puppies that would grow up to be examples of the written standard of the breed.
Many things must be taken into consideration. First, you must know what to look for in a reputable breeder. No one wants to admit that they are not reputable. You have to find out on your own. To know what a grown dog and a puppy should look like, obtain a good breed book on the Great Dane. There are many available in the pet stores and they will include the standard. Read it through. Then read it again, paying particular attention to details. Now, for the breeders.
Check the paper ads. Write them all down and call for some basic information such as age, price, shots, wormed, cropped, dewclaws removed, registered with papers in hand for you to see, pedigrees for you to study and keep, pictures (if not the real thing) of the parents along with statistics: age, weight, temperament, trainability, health, show wins (if shown at all), address so you can see for yourself.
Much of this can be learned upon visiting the litter, in fact all should be obtainable. BEWARE the breeder guaranteeing show quality, no hip dysplasia or any other problem. The only guarantee for this would be replacement pups or money back. Parents can be certified clear of hip dysplasia by OFA (not the vet), and should be, as this helps immensely in breeding pups with less likelihood of developing the disease, as does using dogs that have CERF registered eyes, heart and thyroid normal (special tests) helps prevent any of these problems from being passed on down the line. Take the case of HD. Because a dog has "not produced any with HD" does not prove the dog does not carry HD. Besides, these people that say that never follow-up on their puppies, so they don't know if it was produced. And they usually refuse to have their own dogs checked by OFA. As a puppy, show quality is about color ONLY. If it grows up without any faults listed in the standard, it can then be shown (but not necessarily win). The finding of a really show quality pup is usually by luck and a lot of breeder experience to know what they produce.
Feel free to ask the breeder any question. They should answer promptly with the truth or find out for you. If you feel they are hiding something, pushing a sale, or will easily lower the price to get rid of the dog, then you should look elsewhere. A reputable breeder keeps only stock they are proud to have. None will 'sacrifice' or 'have to sell' a dog...or they should do no breeding if they haven't the facilities to keep the stock. They should screen the buyer to be sure the pup will have a proper environment to develop in. If the buyer is not suited to the pup, the breeder should not sell. Those who sell to those for money alone are not breeding for quality, just quantity to produce more bucks. The cheaper the dog, the less you are getting.
(The following material is taken from a lecture by Dr. Finco of the University of Minnesota Veterinarian School).