Good breeders...
Breed for a reason other than selling puppies, usually to get a puppy for themselves to show, work or take part in an activity, breed from fully health tested dogs and pick the stud carefully to get the best mix of traits...not just two dogs they happen to own, so it's unlikely that they own the stud as well as the bitch.
They register the litter with the relevant organisation (usually kennel club) because there isn't really any good reason not to.
They usually breed once a year or less often, breed the bitch only between the ages of 2 and 8 and leave a year between litters.
They usually have a waiting list for litters well before the mating actually happens.
They should grill you about your household and lifestyle and will want to meet you all. They should be not only willing but keen to show you all relevant paperwork and discuss health test results. They should tell you that they will take back the puppy at any point if your circumstances change and it needs to be rehomed.
The bitch and puppies should be wormed regularly, they should be fed a decent quality of food (not something like bakers or pedigree) and they should follow a socialisation plan for the puppies.
They will usually pick which puppy suits you rather than whoever pays first picking and will want to keep in touch to see how your dog gets on.
They should give you some sort of puppy pack, including insurance and food so there's no disruptions to the puppy and they don't usually vaccinate because different vets use different vaccines and it can muck up the schedule.
Some of that may be UK specific...but tbh I can't think that much would be.