Aloha and Welcome! :wavey:
You are asking really good questions; I'll do my best to answer them ... .
I am headed to Disney soon and want to
sell some of my really rare pins
AND I also want to trade some of my hard to find pins for pins that I can trade at the parks.
What is the best way to do this? I don't want to purchase a book and then hear from people saying it varies, but I know that some RARE pins must have a value range...
How do you know who to trust for trading pins? I would be sad if I traded a hard to find pin for scrappers.
Is there a set of rules for listing trades?
what are the descriptions that are used? I have some mint on card never removed, some limited that were from park trade this Feb. (so not mint) etc.
There are two ways to sell your pins, on eBay and on private forums, like here. I am not an eBay seller, so I don't know too much about the former, except there are two types of auctions - the regular auction (a reserve - the minimum you are willing to accept for an item - can be set) and the buy it now (where you decide on what you want for the item ahead of time, no bidding required) and you can list an item with both regular bidding and buy it now at the same time. If you choose to sell your pins here, you need to know what you want for them in advance and quote your prices clearly (however, you can modify them as your sale goes on). You can consult closed auctions on eBay or Tomarts (although I would take the latter with a barrel of salt) for a guideline of what the pins could/should be worth - or you could just ask people here for their opinions.
Knowing who to trust for trading pins is a good question. If you are trading online, your best bet is to check references. If you are trading in person, that's a bit harder. Then, you'll just have to look at the pins you are getting, what you are giving up, and ask yourself if the trade makes sense. If something seems 'off,' if the trade seems too good to be true, if the other person is too pushy to get you to accept the trade, or if something (for any irrational or rational reason) makes you uncomfortable, you probably are right and should pass on the trade. Never make a trade unless you are 100% comfortable with it. Don't feel that you must accept every trade offer that comes your way and remember that a polite 'no thank you' is just as acceptable an answer as a 'yes, please, I'd love to trade.'
As far as I know, there is no set rule for listing your traders. Just start a thread, mention what you've got to trade ... and what you are looking for specifically (if you are looking for any particular pins) or your Pin Pics account ID so people know what to offer you and hope people will get in contact with you. Most people use the descriptions that are on the Pin Pics listings, but sometimes they write their own, particularly if the pin isn't on Pin Pics.
I hope this helps and, again, welcome!