I've seen threads on here selling WoW tokens and was unaware it was even possible to trade them in game. How do you go about executing these trades on here?

You give the person buying the "token" the amount of gold it is worth.

Then they buy the token and use it towards their account.

So they would have to be on the same server as you? The threads i see on here make no mention of servers.

You just make a level 1 on the server where they have gold and buy token on the level 1.