First off, I wanted to say that I had a great time at this year's Dexcon. I played in many events that were well run and had much fun; however, there were a few events that I was very disappointed in. The main problem with these events was a too casual attitude and lack of preparedness on the part of the GM. We are all at the con to have fun, but it is important to keep in mind that most of the players are paying customers, so GMs should adopt a serious attitude in doing a good job running their events.
Some behaviors that I have observed in this and recent cons:
-GM shows up late to the event and/or does not have game set-up on time
-GM missing materials needed to play the game
-GM does not know the rules of the game
-GM does not take enough time to explain the rules
-GM makes up rules on the fly
-GM wanders off during game or deputizes a player to run the game (and then disappears)
-Game scenario is totally unbalanced/not playtested
I was going to write up a list of GM Do's and Dont's, but fortunately folks who are much more articulate than me have already done so. Below are some links with helpful information and tips on GMing at a con.
How to Run a Great Convention Game (The Colonial Angle)
http://home.comcast.net/~theangle/congames.htmHow to Game Master at Conventions (Roleplaying Tips)
http://www.roleplayingtips.com/readissue.php?number=430#tipsThe Dos and Don'ts of Game Mastering a Convention Game (Rpg.net)
http://www.rpg.net/columns/oneshot/oneshot17.phtml6 Rules for GMing Great RPG Events at Conventions (Gnome Stew)
http://www.gnomestew.com/gaming-conventions/6-rules-for-gming-great-rpg-events-at-conventionsThere is also a yahoo group covering this topic called GMSN (Game Master Support Network), and there are many guides posted there as well.
http://games.groups.yahoo.com/group/GMSN/Regards
-Rob