Disney CMs and most pin traders will trade pins marked "Disney" on the back for similar pins. For example, you can trade a metal/cloissone pin for a similar one, but not a plastic pin for a metal one. The CMs wearing lanyards can help you out and you can get some good advice at any Pin Trading Station or cart. I highly recommend talking to the CMs that staff these locations... they can often clue you into what's "hot", what's just been released, etc.
As for trading... don't be too scared to wear your lanyard/pins. If you are not interesting in trading, but only displaying what you have, when someone approaches you, simply say, "These are just for display, thank you" or "I'm not interested in trading these; they're keepers". People understand that ... usually my "traders" are on the left; "keepers" on my right. So when someone asks, I just tell them that. Saying "no" is perfectly acceptable. After all, they are your pins.
I trade mostly with CMs ... mostly at pin stations. I'll ALWAYS trade with a child and they can pick a "keeper" or a "trader" from my lanyard. Pin trading for them should be a magical experience... and I can usually replace the "keepers" with a little effort.