Though the safest thing to do would be to not allow new users at all and creating accounts for your users, the above will at least better your chances of not being busted. The fifth step is to voice validate all new users. If they leave you a voice number then call them up and talk with them for a little while. Finally, if you are a sysop who runs a board that deals with Credit Card numbers then your days are numbered. Not only should you lose them because you will get caught but also because it is immoral.
Most people never think about what happens after they card some new equipment.
They figure they have just ripped off a company which makes a living by ripping off other people. This is true to an extent however you are making things very hard on the people who own the credit card which you stole. When Credit Card Fraud is committed, the first suspects are the owners of the credit card. The police normally obtain a search warrant and tear up the home of the owner searching for the equipment while the credit card company doesn't even care about this because they figure it is the owner's fault that the card number was stolen. This is a shitty thing to do because the people do not deserve to have to put up with this.