What kinds of activities do you do with your dogs?
You should get an answer to this question. Even a private breeder should have some answers. Look for some kind of answer that involves socialization of the dogs. Going to the dog park and taking walks are all perfectly acceptable answers from a private breeder. If the breeder is stumped on how to answer the question (and possibly ignores the question entirely) the definitive answer is “I don’t do anything with my dogs. They’re livestock and produce puppies for sale”. This is a breeder you will want to avoid. And this answer, either stated or implied is a deal-breaker.
A private breeder should be keeping her dogs’ training up and socializing the animals regularly. Even a large kennel full of dogs should be getting regular attention, exercise and socialization. They are social animals and are being produced to live with human beings. They are not livestock being raised to live in a barn. Apart from being cruel to the dogs you want to avoid this breeder because they will not know their dogs inside and out if they don’t use them for anything or spend time with them outside the kennel or house. Also being out in the public eye means there is some public oversight of this breeder. It helps to affirm the dogs are controllable, clean and neat and possibly friendly as well.