Sorry for the noob question. I have never tried to sell or trade a firearm at a gun show. I want to try and sell/trade a nib Colt 6920 at the Ho Co gun show this weekend and want advice on how to do it and not get in trouble with MoM's goons.
Offer it for sale- once you've found a buyer and determined price-
option 1- find a FFL that is local to the buyer there and process the paperwork. - there will be a fee for it, and generally the FFL will take possession of the firearm for the 7days 120+ days wait. (Get full payment for the rifle before turning over to FFL & make buyer pay FFL fees.)
Option 2 - head to local MDSP - (search for a thread on how best to do this) and do paperwork there, you maintain possession of firearm until after 8day period is up. Transfer firearm, sign paperwork, send paperwork to MDSP. (Take a large deposit or full payment upfront, collect remainder at transfer.)
(I'd also put on your "for sale" sign - FFL REQUIRED. )