You start by looking for a breeder and then waiting for them to have a litter rather than looking for a puppy. That usually (though not absolutely always) means you’re going on a waiting list for a planned litter some point in the next year or two.
You’re looking for someone who breeds because they want a puppy from the litter to do whatever it is they do with their dogs (showing, a sport, working).
The breed club is usually the best place to start.
You research all the appropriate health tests for the breed and when you ask about them, they should not only be happy to discuss them, but will have the paperwork for them... they should want to know about your set up and some actually have questionnaires or other things like that to find out about you, but equally should be happy to answer any questions you have. They’ll also insist (sometimes with a contract) that if you ever need to rehome the puppy for any reason that you go to them first.
They’ll likely have more dogs than an average person, lol, but usually between between 5 and 7, 2 or 3 of breeding age, a couple too young and 2 or 3 too old because they’ll only breed every couple of years. Those numbers aren’t exact, but... if they’re breeding several litters a year or they rehome the dogs when they’ve finished breeding dogs then they’re big red flags and if they have loads of dogs then they’re probably kept outside and that again (with the exception of working dogs that you’d probably not want as a pet anyway) that’s a massive red flag.
They’ll usually not own the dad, because it’s hugely unlikely that they just happen to own a dog that has traits that complement the bitch. If they’ve just got two pet dogs they’re breeding for the hell of it, some people are ok with that, but it can cause potential issues for a puppy owner.
Kennel club registration is really basic, but if they’re an eligible breed they should be doing it, there’s no ok reason not to and it means you can check the health tests and the inbreeding coefficient yourself online.