1. Know The Player Characters
The PCs are the players’ interface with your adventure. If there’s one bit of preparation you can never skimp on, it’s the player characters. You don’t need to memorise everything, but you need to remember any key plot hooks or powers that you can use to bring that character into the action. Point out places where a particular PC might use one of their abilities (“hey, your spy has Traffic Analysis, so you can intercept the bad guys’ radio communications and work out their movements”) and things they need to know (“as a Paladin of the Great Gold Wyrm, you probably know someone in the Imperial Legion. You could try tapping them for information”). You can’t rely on the players to volunteer information like they might in a regular campaign game.
2.Go Around The Table
At a table of six, you’re going to have a mix of players – loud ones, quiet ones, shy ones, dominant ones, rules-lovers and people who don’t care what dice they’re rolling, combat monsters and character actors, hardcore fans of the game, and people who wandered in because there was a free spot at your table. It’s easy to fall into the trap of catering to the really enthusiastic, engaged players at the expense of others. So, always go around the table and make sure all the players have the opportunity to get involved in the action. Suggest ways for them to contribute if necessary.
Also, go physically around the table, especially if it’s a noisy room. If you need to have a one-on-one conversation with a player, don’t shout across the table. Get up and walk around to that player if you can.
3. Observe The Rules
Don’t necessarily obey them, mind, but don’t completely ignore them. Many people play convention games to see how a particular rules system plays. They want to see how the game works, especially the elements that are especially thematic or distinctive. For example, you can run an Aliens-inspired bug hunt mission in any science-fiction rpg, and it’s always a good model for a convention game – but show off the distinctive elements of your game of choice in the bug hunt. An Ashen Stars bug hunt might highlight the use of investigative abilities to find a way to escape the remorseless aliens, while a Gaean Reach bug hunt might spend more time talking about how this is a trap set by the hated Quandos Vorn.
4. Beware of Time Dilation
In a four-hour convention slot, you can assume that the first 30-45 minutes are lost to late arrivals, reading character sheets, introductions, trips to the bathroom and/or snack bar and other administrivia, and you should aim to finish up half an hour before the end of the slot, to give yourself a buffer in case scenes overrun, players need to leave early, and to handle any post-game debriefings. That leaves you with a shade under three hours of actual game time. Expect your first few scenes to take much longer than planned, as players struggle to find their character’s voice and role in the group, and to get to grips with the setting. Expect later scenes to go much more quickly than you’d expect, as convention players take bigger risks and make grander gestures than they might in campaign play.
5. Be Prepared!
Character sheets, dice, pencils, scratch paper (enough for you and the players), copy of your scenario, enthusiasm, quick-reference sheets, a rulebook, bottle of water, more dice because the first lot are going to roll under tables and get lost, more enthusiasm. Phone, set to silent. Throat lozenges, because you’re going to be hoarse after running a few games. Get some sleep and eat some real food if you can manage it.
In extremis, enthusiasm may be simulated with sufficient sugar and caffeine.
6. Let the Game Breathe
Part of your role as a convention GM is to make sure that everyone has a good time at your table. Sometimes that means giving the players things to do by throwing interesting NPCs and mysterious and action scenes at them, but it also involves stepping back when the players are having fun just roleplaying their characters or planning their next move. If everyone’s talking animatedly about events in the game, just step back for a moment. This can be hard to do in the heat of the moment, especially with that remorseless clock ticking down towards the end of the slot, but it’ll pay dividends with a good table players.