
Health test results. If you want a pup to show then you might want to know how the parents have done in the ring, or if one for work then how good they were in that sphere.
Preferably the breeder should be knowledgeable in their chosen breed so that they can offer you the necesary support. If they are a first time breeder you would want to know that they have bred with the mentoring and back up of someone very expoereinced so that they can still offer you this.
You also need to like the breeder, after all they will be your first port of call if you have any queries.