The main thing to look for is that the dog is well bred, meaning CAREFULLY bred. The pedigree is only meaningful insofar as the names on the paper mean something to people who know the breed. They can look at a pedigree of a puppy from parents they've never seen, but know 2 of the 4 grandparents and dozens of the other dogs on the pedigree. They know them because they've seen them, they watched them grow up, they know what they eventually died from, if they were friendly, if they were spooky, if they were gorgeous puppies who achieved their championships early but can barely walk at 4 years old, etc. That's the true use of a pedigree.
A good breeder will know if 1 of the grandparents of the prospective litter has temperament issues that make selection of a mate with super stability more important than other objectives. They will know that one of the sides of the family has cancer issues, or joint issues, and seek a breeding that brings in generations of dogs tested and clear for that issue.
The problem with people who don't show and don't do health testing (a simple vet check is not sufficient -- most breeds require hundreds of dollars in pre-breeding health clearances done, sometimes annually. EKGs, echocardiograms, hip and knee x-rays, blood testing, etc.) is that they don't know WHAT mixture they're coming up with.
The appearance of health is no guarantee that the offspring will be healthy at the age of 2 or 3. A breeder who can show you pictures of the grandparents and great grandparents of the litters (or introduce you to the dogs themselves) running around at 6-10 years old and older, and evidence that she is actively seeking out signs of health issues and not breeding such dogs is offering a better bet.
Remember -- all puppies are adorable. This will be a member of your family for a significant part of your life -- it's worth a few extra months to find the best possible match.
This is one of the best website resources on dogs I know of -- enjoy researching!
http://dogplay.com/GettingDog/index.html