You can't, just like anywhere else.. here, ebay, wherever. That is up to the user. It's like asking you to prove to me, you are who you say you are. Can you do that? IMO, the most important thing is the security of the payment method.. which is why the site recommends PayPal. I don't really care who you are, but if I buy something from you I will use PayPal because it provides me and you with full protection.
This is just a reminder that the $10.00 New Member credit ends on opening day which is in 2 days, the 12th of December. So if you are thinking of joining the site you may want to do it now and get the $10.00 credit which does not expire and can be used at any time.. This way it costs you nothing to try out the auction site and sell a few items. 73, Andrew AD5KO