While there definitely are some bad apples out there, I have truly had some great experiences with various breeders around the country. I think it's most important to establish a conversation about the animal before any payments are made, and get all the information that you can. BOI on Faunaclassifieds is a good resource, as well as simply googling the name.
One thing that I highly recommend is to NOT have any animals shipped directly to your home, but rather to a FedEx or UPS facility instead. Once you receive the package, open it IN the store, not at home. This way if you open the box and the animal shipped does not match the description or expectations, you can refuse to accept the shipment, and not take the animal into your possession. This leaves no potential questions as to how the animal was treated or cared for while in your home.