It's difficult OP.
I am quite rural and here it was word of mouth. Saying that, I have become close friends with her and we have done two litters together, I have rehomed an ex show dog of hers and she has helped me with a litter from my own.
One point someone said on your other thread was that a good breeder would never have two litters at the same time or close together. I would disagree with that. She spends over half the year travelling to shows, including abroad and lecturing at breed events. She has fifteen dogs of her own. What you often find with bitches is that they come in together, both mine are in season now.
So in her case she would take two litters close, if the dogs were ready, rather than take one when she was not going to be there.
She has a list as long as my arm of people looking for puppies. She gets them very carefully, almost as intense as the research people suggest you do when buying a puppy. If she did not know them. References, home check etc.
It still falls down. She has a dog back with her now, perfect home. The lady lost her husband and had a breakdown, she could not cope. Dog goes back to her no questions.
She would be able to tell you where every single puppy she has ever had is, and keeps in touch with them all. Maybe not regularly but from time to time.
She is exceptional in her knowledge and kindness towards dogs. I asked many people when I was looking and her name came up time and time again. She has never advertised a litter, just takes details if you call and when something comes up she will contact you.
Again with being rural a lot of farmers and gamekeepers breed good lines of puppies from labs, to spaniels and collies. Again, rarely advertised and a lot of word of mouth.
There's been a lot of fear recently about advertising puppies following an increase in thefts. There was a case in east Lothian recently where the puppies were taken but thankfully found.