the concept of ATC is the person-to-person trade, as well as trading by mail. the most fun is to trade person-to-person though. the basic idea is the card-for-card trade. [although sometimes some people think one from their cards is worth more than one from the others - mostly with the argument that they put more work into their atc.]

WHERE TO TRADE YOUR CARDS
so far there are two ATC centers which organize Trading Sessions on a regular basis: one in zürich and one in calgary. the idea of the centers is not the private collection (there are many of those around of course) but the communication. the centers are open to the public and they also organize the ATC Trading Sessions. the centers are places to communicate the idea of trading cards and to hold the events.

TRADING SESSIONS
hopefully there might be more centers soon : ANYBODY CAN ORGANIZE A Trading Session. the only stipulation is a certain continuity (eg. every month on a regular day).
the different ATC centers inform each other as much as possible - so we can exchange ideas and experiences.