Hello sam08223,
Welcome to the board! Make sure know what you're getting into, cause you'll get completely hooked in no time!

I'll try to answer your questions as concise as possible:
Any special web sites that are better than others?
Well, not really. All the pin sites I've been to are kinda different from each other. The one site that people trade the most with would probably be pinpics. com and dizpins.com. Check them out and feel free to ask questions.
What makes a pin "special"?
This is a loaded question....

... I think the best way to answer it would be, what ever pins you like....

... Because each of us I think had been through the phase of buying all the LE pins and finding out that being an LE pin does not mean it's a hot pin. The low edition pins are most of the times pretty tradeables, while certain characters are always good traders. For example tinkerbell, NBC, and Villains pins.
And how do we trade over the net?
You could start by going to any of the pin trading sites (disboards.com, dizpins.com, pinpics.com, dizneypins.com, etc. etc) and list what you want and what you have to trade. You'll usually get some people to start trading with you. Some of these boards offers third person trading, which helps with new traders without references to start trading. Sometimes people are not so comfortable trading without references.
Anyways,
I hope this helps and good luck with your new hobby..... watch out for sizzling credit cards!!!

Feel free to post any questions.....
cynthia