First lets do a little more homework. Careful observation is the key. Have a list of questions to ask and do not be afraid to ask them. If the answers are short or non-existent, thank them for their time and move on to the next shop. If a pet shop or breeder does not have the time to answer your questions, most likely they will not to be available when you have problems either.
Many breeders now practice the closed aviary concept.
No new birds are allowed into the aviary unless stringent quarantine methods are practiced. Many times the guarantee on closed aviary birds is much better than you will find at other places because the risk of disease has been drastically minimized. How you will view the birds available is up to the breeder. Health of the bird should be the number one consideration. Check out the environment in which the bird is being kept.