Off the top of my head...these are some of my several questions I asked when I was looking for my first Yorkie.
I asked:
-for a current picture of the puppy available
-his current weight
-his expected adult weight
-when he'd be available (he was a show prospect, so I had to wait until he was 5-6 months old)
-about his temperament
-weight of his parents
-whether there's a health guarantee, and if they do, what it entails
-whether there'd be a written contract agreement we'd both sign (protection for both sides)
-questions on health issues risks (liver shunt etc)
-whether he's been microchipped
-whether I visit and see him
-whether I could meet the breeder at their home and meet the puppy's mother (knowing that the sire was from another breeder - a good sign of no inbreeding)
health test / status on the mother/sire and grandparents etc
-how long the breeder had been breeding for
-how long the breeder has been showing competitively for (I did my own research and asked other breeders whether they knew of my breeders for my own peace of mind)
-how long their Yorkies live until
-vet reference
-shots and rabies certificates
-breeder's name of the sire
I didn't ask all questions at once. At the same time I made sure to offer information about myself to ensure they knew who I was and how responsible of a dog owner I've been in the past and how their puppy would be in perfect care in my home.
I think you have to gauge it, depending on the type of people the breeder is. Some have formal application forms required from you. It's kind of like a baby adoption process where they screen you to make sure you and your home is suitable to care for their babies, you'd be a responsible dog owner, and that you're not crazy.
