One piece of advice i have heard is when you get the package, and you sign for it, go inside and without opening it write "RETURN TO SENDER" on the package. This way if 30 mins later an officer decides to knock on your door you can say you didn't know what the package was and just give him the package to inspect. This way he will see you didn't open it and were planning to send it back.
I've also heard that 99% of places that ask for a credit card number are scammers. I've heard western union is how most legit places do business. Also remember when buying overseas that you have to deal with customs and alot of sites that you have probably already visited are on watch lists.