If there is someone that has a puppy or dog listed for sale and it appears to be a scam, I have learned a couple of different ways to check it out:
If they say the dog is AKC you can verify the registration number by going on the AKC website and do a lookup on the number
http://www.akc.org/store/free/ click on dogs lookup and fill in the info. If they tell you the puppy does not have a number yet because they haven't been registered, ask for their parents' numbers. It should still tell you what type of animal the number is registered to and what the animal's name is.
I have also done reverse lookups on phone numbers to see if there phone number matches the area they say they are from (even if it is a cellphone, it will tell you what area they phone number is based out of)
http://www.411locate.com/
If they ask you for your phone number, don't give it out. Instead, you ask for theirs and then you can look it up.
Hope this helps....
Jan