Hi! When we were planning trip number one I knew nothing about PT either. First I went to the main WDW website and searched "pin trading". From there I opened up a link that had FAQs in regards to PT. I am sure that if you put PT in a search on the Disboards you will get many responses as well. I will attempt to explain it a bit on here... it is really simple and you will get the hang of it quickly!
Here goes:
1. First of all you need pins and a lanyard to start. These can be bought online at the Disney site, in the parks, or many have had good luck on ebay (but there are cons to ebay as well). You can even get starter sets with several pins on it!
2. In the parks, many WDW restaurants, at Downtown Disney, and in WDW stores/giftshops you will see CM's with trading lanyards. Blue can trade with anybody, green with children only.
3. If they have something you like... they have to trade with you!
4. You cannot give them a pin that they already have displayed.
5. All pins that you trade (buy) must be copyright Disney.
6. Trade for what you like! Some people do a theme (like Tink or Pirates), some only look for "Hidden Mickeys" or "Cast Exclusive"... it is just a matter of preference.
7. It is addictive!

You find yourself scoping out all CM's for lanyards (some do have pouches near their waist)!
8. It is simple to do, you will have the hang of it in no time and young kids even do it!
Have fun!

Feel free to ask anymore questions... if I don't have the answer someone on here will!
