How to run a Con Game Badly

You know, running a con game badly is a fine art and one which I think few people spend as little time on as they could. Con games are a way for people to try new things and play with new people and have new and exciting experiences. It's really important to scotch all that as fast as you can. Since, I'm all about the helpful tips, Away we go!

Pregens
You know, Everybody loves bashing a character. Even people who've never played an RPG before find that making a character before playing the game is sooper cool. Possibly the best part. Certainly better than playing the dumb game anyway. So in any game that you run for a convention, You should never prepare pregens for your players. Skindiving into a ruleset is big fun. And as an added bonus, There is absolutely no way to predict what sort of characters the players will come up with. (Although, seemingly, there is a statistically significant probability that you will get at least one fat guy who wants to play a lesbian catgirl stripper ninja. Doesn't really matter what game it is.)
Of course, since game time is fairly finite, you'll want to stay away from game systems that are actually fairly easy to make characters in a few minutes. You'll want hours of happy character making action. Another way to stretch this out is by having only a single copy of the core rules.

Rules
And while I'm on the subject of rules, You should definitely pick the most abstract and abstruse ruleset for a particular plot that you can find. You can always list it as a "Beginners Game" for maximum effect. If you only want advanced players in your game, then how will your game become more popular? Creating a game that's easy for beginners to learn is a fine art. Don't practice it. Forget Teenagers from Outer Space or TOON. Immortal, the Forever War, or Aftermath is where it's at.

Preparation
Improv is the soul of the con game, As such it is important to remain carefully ignorant of anything that might get in the way of your freeform loosey goosey style of GMing. As a result, You'll want to be very fuzzy on the details of the adventure and completely foggy on how the rules actually work. Alcohol might help this process. Sleep deprivation is also good for this.
Also, it cannot be stressed how important it is to be free of the shackles of printed up sheets, dice, writing implements, or any other accoutrements that could bog you down.

Structure
Okay, It's important to realize that narrative structure is a trap. Having a beginning, a middle, and an end to your adventure is SO done to death. So, what's obviously called for a long pointless and meandering kind of plot with little in the way of actual action (Although, some do swear by a large chunk of pointless combat.) cause that kind of game is DA BOMB.
If I were you, I would create a plot that requires the PC's to be led around by the nose at all times, to do pointless things. I would also make sure that any of their actions are slowed to a crawl by dint of absolute ignorance of the concept of pacing.
I"d make sure that my NPC's are so much Kooler than the PC's and that the NPC's get to do all the cool things in the adventure. Also, I'd make sure that there was only one path to the end of the adventure and if the players are too dumb to "get it" then they'd just have to remain stuck where they were. Dopes. Extra bonus points if you can do this in a dull monotone.

Shills
You should definitely use every means at your disposal to make sure that the people that you play with regularly have prominent places in your con game. They should have the opportunity to play important "NPC's" in your game. Hey, maybe it would be a good idea to have them be a GM plant and at an important point of the game, start sabotaging the players and killing the other PC's with obvious GM collusion. That stuff is killer.

See! Wasn't that helpful?

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