I always always always recommend looking at the German Shepherd Club of America first and foremost. For one thing, the breed clubs often offer a stricter code of ethics in which the breeder must follow. It's often breed specific, and, imo, anybody who is a member of the GSCA is probably reputable. As always, keep your eyes open to red flags and check out their OFAs, PennHips, CERFs, and other important tests. Do they show? What other activities do they do? etc. Good Luck!