Procedure on trading watches?

[psharpless]

I am considering transacting some watch business with others on this forum. Obviously, I would only deal with persons who I think are legit, like some that are frequently named on this forum. I was just wondering though, what's the best way to protect yourself when trading watches with another person. How do you decide who first sends their watch to the other party or do you send at the same time, same method? What's the best, proper and legal way to establish proof you sent a watch to someone? Thanks in advance to some of you veterans who do this a lot!!