I've gathered a number of resources below in regards to creating and running a Convention game scenario. While I'm not going to reiterate everything you can find in these resources, I do want to include what I view as the Top Ten Essential Points to Running a Convention Game, regardless of the gaming system.
- Have Fun: Whatever happens, so long as you and all of the players at the table are having fun, then they will walk away with a great gaming experience. This is the ultimate rule for running convention games, and all other rules are intended to help you accomplish this goal.
- Use a Simple Scenario: Create a scenario that you intend to be run from beginning to end in 3 to 3.5 hours, assuming a four hour session length. Generally, these scenarios are fairly linear, limited to 3-5 scenes, and have a reasonably limited focus.
- Be Prepared: Have all of your materials ready. Know your rules. If you don't remember a particular rule for a situation that will be occuring in your scenario, make crib notes so you don't have to interrupt the game to look up the rule.
- Use Pregens: Use pregenerated characters if at all possible, and generally speaking, it's always possible. Creating characters in the session steals time that could be better spent actually gaming.
- Move the Game Forward: Your scenario should always reward forward motion. Many players are aware of the time constraints, and feel that they are entitled to a complete scenario with a beginning, middle and end, all within the time allotted for the game. Letting a game stall for something like shopping for magic items or gathering rumors that do not contribute to moving the scenario forward goes against this general expectation. Don't be too subtle in your clues.
- Keep Them Alive For Most Of The Game: Remember that you are running games for people who paid to be sitting at your table. As the customer, they expect their money's worth. As the GM, you should aim to keep them alive for most of the scenario. Aside from a series of poor rolls and even poorer decisions, a character should really face death or some other form of removal from the scenario until the climactic final scene (or more than two-thirds the allotted session time has passed.) If death is a regular occurrence over the course of a scenario due to the setting or the system (such as the use of clones in a Paranoia game), apply this rule to any condition that can remove a character from the scenario permanently.
- Be Prepared To Skip Ahead: Even if you plan for a reasonably short scenario, you may be running for a group that pushes the envelope and really drags things out. Be prepared to skip ahead to the final climactic scene if they haven't gotten there when you are an hour or so out from the end of the session. If you didn't design your scenario with that in mind, you should at least give some thought as to what you can drop if you need to make adjustments.
- Be Prepared To Stretch It Out: Sometimes you may create a scenario that, in the hands of the gamers at your table, reaches the end too quickly. Be prepared to introduce one or more minor scenes or obstacles to add to the length of the scenario if the players move the game forward too quickly. Finishing a complete scenario in two hours can be rewarding, but if your players paid for four hours of gaming, they may be disappointed. Even if you don't have this as part of your current scenario, you should at least give it some thought ahead of time so you can be prepared, just in case.
- Avoid Breaks: Taking breaks in mid-session always tend to last much longer than you plan, and that impacts the time spent gaming. With that in mind, you should do what you can to avoid breaks in mid-session. Go to the restroom before you get to your table and set up, just to make sure nature doesn't force you to interrupt the flow of your session. If you think you'll have to take a break, plan for it and be strict on your starting time when the break is over.
- Pretest Your Scenario: If at all possible, run the scenario at home with another set of players before taking it out to a Convention. This allows you to see what works, what doesn't, and what might need to be modified or expanded to make the game even better.
Hope This Helps,
Roleplaying Tips Weekly Supplemental #8: "Running Games At Conventions"
Gar Hanrahan's approach to writing con scenarios
In Like Flynn: One Shot Adventure Creation
How To Run a Great Convention Game