The parks and DTD sell pins in many of the shops of course, but in each area there is a central pin location with a larger selection. In HS, it is under the Sorcerers Hat, in MK it is in the Trading Post, in Epcot it is in front of the Fountains/ between the Breezeways. I confess...I do not remember where it is in AK. At DTD, it is at Pin Traders. In these areas, pins are usually purchased and pin enthusiasts and new pin traders can also consult with cast members regarding pin releases and Limited Editions, etc. (there is a binder in these locations with this information). Many Vacation Club and Annual Pass Holders or D23 folks come for specific pins as well. As far as trading goes...most Merchandise cast members wear a hip or neck lanyard and are given a specific amount of pins to wear on it. Any Guest who desires to trade with a cast member need only ask, and they trade a pin for a pin, up to 2 pins at a time. The only rules that I know of are this: the pin must be a Disney pin (logo on back surface), and if a cast member already has that specific pin on their lanyard, then they are technically not supposed to accept a duplicate, but I have seen this happen. Guest may also trade with other Guests. There are certain lanyards which are green, and the cast members who wear these trade with children only. It is a lot of fun and can be very addictive, haha. People get very specific as they sometimes chase sets of pins/hidden mickey pins and they spend the day doing it, too! The hardest part in Merchandise is this...I cannot tell you how many times a Guest has approached me in the middle of a transaction to ask to see my pins. My rule of thumb is this...the Guests waiting for me to ring up their purchases come first. Unfortunately, the pin trader needs to wait. They don't always want to...I try to address the pin thing as quick as I can, but you also cannot have 8 people get upset because they are also waiting for your attention. Gets tricky sometimes!