For a specific answer, it depends on what breed you're looking for.
For a general answer, try to find like minded people, whether in person or online, and find out who has a dog that does great work in the field. Every owner thinks their dog is the best and every owner is right :D so get started by putting the feelers out.
For me, I have labradors. We've had them since 1985. I was born into a hunting household so I'm in a few circles where I could ask around and see who has what, which dogs are working well, and whose dogs have characteristics I like in the field. For me specifically, I don't need a fire breather to break sound barriers when retrieving. I DO need a dog that is quiet, patient, steady and willing to work. I like quick, careful QUIET dogs with good noses. I also compete with my dogs and every dog in that catalog is registered with the CKC, AKC or UKC. Start pulling catalogs and watching kennel names and you'll get a feel for who to reach out to. Breed clubs can also put you in touch with registered breeders (the Lab Owners Club, the Golden Retriever Club of Greater Toronto, etc) but you do need to specify you're looking for a hunting dog. Again, finding events those clubs are holding, getting out to the events or training days, taking a look around, all these things can help you find a registered breeder. Then put more feelers out and see how people feel about the breeder and their dogs. Everyone will have an opinion and it can be tricky to separate fact from fiction, but any of these things I've mentioned can help you get started with your search.