thekimballs has given some really good info on looking for the right breeder. At the beginning of the year, we were looking for a Cavalier King Charles Spaniel. I researched the breed first, then breeders. Let me tell you, the worst ones are the ones that look good on the outside. I nearly bought one from a woman who had some pretty good lines, but for some reason, I had red flags about her. She said that all her puppies were home raised w/children. She gets all their vaccines separately to be easier on their systems. She lets the puppies self wean before they are allowed to go to their new homes.
Later, I noticed another ad for a different breed of puppies being advertised with the same phone number.

I thought she only bred Cavaliers. Well, as it turns out, she sells Cavaliers, Pugs, Malteses, and some other breed. All of which are advertised as the only breed in the house. When you call her about her available puppies, she has a sneaky way of making you tell her what breed you are calling about so she doesn't out herself as having mulitiple breeds. Not long after, I found out that this woman goes to puppy mill auctions in Missouri (which seems to be the puppy mill capital :-() and buys a mother and her litter and takes them and sells them as if she actually bred them. After the litter is sold, she sells the mother under the story that she is too old to breed anymore. Worse than that, to keep with her story of only breeding one breed in the home with children, they have a lot of land and a barn. She keeps all the dogs in the barn and when people come to see them, she take the litter they are coming to see and "sets" them up in the house. Most people aren't nearly observant enough to pick up on all of this. It really makes me angry that there aren't any laws to stop this.
In the end, we bought a Papillion from a breeder near to our house and we couldn't be happier. Well, except that she is small, but I guess those things happen from time to time. Either way, we love her to death and wouldn't change a thing.