It's sometimes a good idea to get references from other breeders. Beware, however, of any breeder who has nothing good to say about another cattery. Slander is all too common in the cat fancy. You should ask to see the sales contract before you commit to buying. This is another good way of evaluating the professionalism and motivations of the breeder.
Sales contracts are common, even for pet-quality cats.
Every breeder uses a slightly different contract, so read through it carefully. Avoid breeders who don't have one at all. During that period, you should have the cat checked by your vet, and tested for FeLV, FIV, parasites, and fungus. Their cats conform to the standards. Their cats are well-behaved, even under the stress of showhall conditions.