Trade safely. Your contact details are only shared with one person, after you accept their claim. Meet somewhere public, never post your address, and remember AegyOrlando never handles cards or money. The rules.
Trade board
Find a card, post a card
Say who is on the card, where it came from, and what you would take for it. When someone claims it and you accept, the two of you swap contact details and sort the rest out yourselves.