@seadog1977 yes of course, it will be breeder specific naturally but I can give you mine.
I met my now best friend many years ago via the breed club. She breeds to an exceptional standard and over the years we have gone on to have shared dogs and litters. Plus our own.
People tend to hear via word of mouth, I have never had to advertise. When I receive an initial enquire we have a basic questionnaire which is sent out. That's sort of background information.
Why you are looking for this breed, what attracts you to the breed, etc.
Then abit about you, your family life, working conditions, jobs, children, garden, etc.
Your history, previous dogs, any specific interests, eg showing, agility.
How you heard about me. This is often handy as a friend of a friend of a friend can reveal a lot.
Then you would go on the list unless that flags any concerns, I will come back to that.
Once we have a litter, which might be a year or so from when you had enquire I would let you know and ask if anything has changed, I would also then ask for two references which I would take up. That's assuming you still wish to have a puppy.
I don't let people chose puppies, I do that and I meet the people at least twice, at mine and if locally at theirs as well. That's not always possible.
I adore my dogs and the breed itself. If I'm selling a puppy it's a lifelong commitment for me to take it back and to support the buyer. I need to match the right puppy to the right person and do my best to ensure it doesn't break down.
We have a couple of Facebook and whatsapp groups for new owners and I have genuinely become friends with all I have sold to. We meet occasionally if in same area and the groups are good for people to interAct and share worries or questions. Puppies can be hard.
I have a breeding restriction on the papers but to be honest that's more to assist with matching if you chose to take a litter. If I had concerns you wanted the dog solely to breed I wouldn't be selling it anyway.
I've turned away more than I've sold by far. I've had to take back two in fifteen years, both due to horrific personal circumstances, death and break down. Both are still with me.
This was a recent enquire which didn't even get a questionnaire, never mind on waiting list.
Word for word.
Hey, here you got puppies. Furloughed and bored. Want to breed and make some holiday money. Will you take back if I'm put back to work full time in office? What kind are they? Willing to pay triple for right dog, great home awaits.
So it's not just breeders who can give dogs a bad name. 
Rocking baby and typing one handed so may have missed bits but think I've covered most of it.