I realize that it is impossible to police an entire community of volunteer RPG gamemasters, nor would anyone want to discourage the volunteer GMs that make the whole machine run. But my expectation of Gen Con is to be able to have the very best gaming experience. And having a terrible, clueless or unprepared GM is a quick way to sour someone's con experience.

I would strongly suggest that Gen Con prepare some sort of minimum expectations that it would circulate to would-be RPG gamemasters as guidelines. At a minimum, I would include:

• Have a plan to fill the allotted time. Realistically, you will need 15 minutes to get going at the start of your slot and to allow stragglers to arrive and 15 minutes at the end to wind down and to allow people to duck out early for their next events. The remaining time is yours to fill. Players at the table should be doing SOMETHING for the remainder of that time.
  
• Plan for players/characters. Every player at your table will need a character for your game. If they are making characters on the spot, bring blank character sheets. If players are expected to bring their own characters, prepare extras just in case they forget. If you are providing pre-made characters, bring copies for the players to hold at least during the game. Ideally, players should be able to take a copy of their character as a souvenir. Players may forget pencils, dice, scratch paper, etc. Have some extras on hand, just in case.
  
• Have a scenario. To the maximum extent the game system allows, have an adventure in mind. It should have a beginning, middle and end -- all of which can be finished in the time allotted. Most RPG scenarios require locales, non-player-characters, opponents, monsters, etc. You should have these prepared ahead of time.
  
• Prepare notes. You should have notes and/or copies of pertinent details about your scenario that are handy and accessible to you during the event. 
  
• Prepare for experience level. If you suggest that there is no experience required and the rules will be be taught, then be prepared to teach the rules.
  
• Character creation. Avoid creating characters at the game table during the event. If you must have players create characters, bring character sheets, pencils, dice and other necessary accouterments for the players' use. Consider bringing multiple copies of the character generation rules for players' to consult.  Prepare a plan to walk players through character creation in a quick and efficient way.
  
• Make it memorable. Players should leave feeling that they have been involved in the highest quality adventure possible. Plan an adventure that makes an impression, whether it be epic, terrifying, hilarious, etc..
  
• Demonstrate the highlights. Every game system has particular strengths and weaknesses. Especially if you are running demo games for a game company, prepare a game that hits the highlights of the game mechanics. Demonstrate the very best, most distinctive parts of the game system. 
  

To your first point, I had several games this year when we ran out of time before we could complete the scenario, but we never had a problem with the game going too short.  Really, I view a game that runs short (within reason, say within 30 minutes of the allotted time) to be an opportunity, not a problem.  It just means that I have time for a potty break, a snack, and an unhurried walk to my next event rather than rushing across downtown, hoping that I can get to the next game before the GM considers me a no-show.

I do agree about avoiding character creation.  I had one game this year where we created characters, which the GM said was to demonstrate how easy it was to do in the game system, but it still ate up a lot of time, and we had to really rush at the end because of it.  In another game, we had characters but we had to equip them, which also ate up a bunch of time, and so the conclusion of the game had to be summarized by the GM instead of played out.  I really think that for a convention game the characters need to be completely finished and ready for the adventure.

Another event mentioned in the write up "This is part 2/3 of a three part module series, you must have played in part A to play this.  Yet we had people show up for them who had not played in the 'required' other one...

I would also say to remember that people are there to enjoy themselves and they have paid money to be at the table.  Plan a scenario in which if a PC dies they have a chance to come back with another character.  I had one of the single worst RPG experiences ever at this Gen Con with a GM who was simply out to kill the entire party,  He was loud to the point of yelling, every other word out of his mouth was the "F" word or another cuss word.  We had a player have a character die in about 30 minutes (of a 4 hour slot) and pretty unfairly.   He politely asked if there was going to be a place he would be reinserted into the scenario and the GM replied "No!  You're (*&$(*Y# dead!!"  The GM killed the entire party in about 2.5 hours with no combat and almost no dice rolling. 

I agree wholeheartedly on the planning a scenario that can be finished in 4 hours.  I would rather a scenario run short but complete than go long and not be done.  As a player I dont mind adventures running short by an hour or less as.  Also, if you are planning a mult-part scenario in which players may be playing in  one part but not another make sure each part is 100%  separate and feels like a complete adventure. 

I would definitely like to build some "best practices for con games" guide, but it's always a matter of the time required to build something robust & useful.

For problematic games, like some listed here, please send an email to events@gencon.com with the details. I do actually follow up on all of them and talk to event organizers and GMs about reports and problems.

-
Derek Guder
Event Manager
Gen Con LLC

Great advice.  I was wondering if I try to squeeze my game into 3 hour but it looks like it shoul 4 hours to leave time for late start and (hopefully) early finish.  I was thinking of running a 1st ed D&D game for teens and older.  Wondering if 6 - 10 PM works better or 7 - 11 PM.  To give people time to get out of the vendor hall and to catch a quick bite.  What do you think?
 

We ran our first Gen Con events last year. Three events per day Thurs-Sun, back to back from 10 AM to 7 PM.

Our game system, Exiles, is more structured than the typical RPG, so it's easier to control play time, but what we did was plan for the maximum time the games SHOULD take and added a half hour on the back end.

We also prepared some 'bonus' content to run in the event that the games ran SHORTER than expected, which with the 30 minute buffer gave us enough time to run another complete bit of content.

I firmly believe that ending early is far, far better than ending late. One might say that people pay for the play time, so you should fill it up, but a complete game is more satisfying and enjoyable than an incomplete one. Players are ever and always good at BSing, and an extra half hour of 'winding down' after the game is over can go almost unnoticed by players.