Puppy!!

I'm thinking of getting a puppy soon. I found a breeder from dog-breeders.biz that's in my general area (well, 2 hours away...). Anyway, does anyone have any idea what questions I should ask or how I can find out if this breeder is on the up-and-up? I've corresponded with her via e-mail several times and she promised me pictures. The puppies will be ready to go in January and they are $600. I want to make sure I'm getting a dog from a reputable breeder. Has anyone ever used this site before or have any suggestions??