The best thing to do would be to contact several breeders and let them know you are interested. They will let you know what litters they have planned, and you can keep in touch until you are ready and they have a litter at the right time. In the meantime, find out as much as you can about the breed, maybe visit some shows and see what sort of dogs you like the look of, and ask questions of the owners regarding temperament, trainability, health etc. You are in the lucky position of not wanting one 'yesterday', as some people expect to get a puppy on demand. Please do not get one from a puppy farm (you call them puppy mills in the USA), go to a breeder who has just a few dogs and rears them carefully as part of the family and does all the health checks. Dobermann Pinschers are superb companions when well bred and well trained, but can be very difficult to manage if you do not know what you taking on.