....this is from the Newfoundland group, but I think it pertains to any breed. I hope the author doesn't mind my cross-posting this but I do think it's really good advice!
Here's a few things that should raise red flags:
1) Remember, anyone can make a pretty web page. Web page programs can be
really user friendly for somebody wanting to design their own. Of course,
you can always ask almost any high school kid to design one for you.
2) I'm very suspicious of web pages that DON'T list the dogs' registered
names. How can you verify anything they claim? This holds especially true
with OFA clearances and AKC titles/accomplishments.
3) I'd also stay away from web pages containing really bad photos of dirty
dogs, pictures of spouses who really don't want to be in the picture holding
said dog still for the photo, cousin Bubba in the background sinking posts
for a new fence, you get the idea.
4) Non-refundable deposits. Excuse me, this is not a special order dining
room table. We're talking about acquiring a new member of your family. Good
breeders with solid reputations usually have waiting lists, stay in touch
with those people and don't need to take your money, thus binding you only
to them. They know that, until the puppies have passed their 10 week cardio
checks, they don't know how many will be available.
5) Ads/web pages that contain the phrase "AKC". That hold about as much
weight as a car ad that says "DMV" (department of motor vehicles). Would
that impress you? Didn't think so.You're paying a substantial amount of
money for this puppy, you expect to be able to register it. By the way, if
the litter is registered with another registering body besides the American
Kennel Club or the Canadian Kennel Club, that's a MAJOR red flag. Puppy
mills register through other organizations because they can't or won't jump
through AKC's hoops. Many have been suspended form AKC.
6) Ads/web pages that say "Ch. bloodlines". Yeah, how far back in the
pedigree? Even the BEST litters contain pet quality puppies. Are those
puppies out of parents who were sold as pets?
7) I'd stay away from anyone who poo-poo's dog shows or regional bred clubs,
labeling them "beauty contests" or "clique-ish". People join clubs to learn,
teach and schmooze; it doesn't matter if we're talking dogs or model trains.
Why show? To have your accomplishment
s judged by somebody more experienced
than yourself.

A good breeder is ready and willing to discuss with you what they hope to
accomplish with this breeding. They're open about their bitch's faults, the
sire's faults, and why they feel this litter will make a positive
contribution to the Newfoundland breed as a whole. Backyard breeders don't
have the knowledge to do so.
9) Experience is what you get when you don't get what you want. Somebody
famous said that, I can't remember who. I include this to point out the
many, many people who found out the hard way that their "caring" breeder
lost interest in them as soon as their check cleared the bank. Ask the
regional club for references, especially ask the rescue people. They're the
ones who get stuck cleaning up the mess.