The learnings from these games are probably somewhat subjective but there are a few trends
1) The Gamers are the Most Important Part: Managing the player group and keeping them both interested and having fun is the single most important part of having a successful game. It sounds really basic, but it really is the key to a fun / successful event. This aspect requires the GM to be a bit of a showman and a bit of a consular.
2) Scenario Design is really important
The structure of the scenario is the next most important aspect of a good con game. Incorporate hidden goals / unknown reinforcements. They're fun when "revealed" and can be used to keep a game balanced and flowing properly. I really like the canard of the "somethings coming over the horizon" to keep my players guessing - it can be the smoke from a distant ironclad, French reinforcements or a Giant Red Dragon, which was used in my historically accurate DAK & Dragon games this year.
I also prefer a three-way fight vs a standard 2 way contest - Having the players need to fight both each other and a GM controlled force creates a very dynamic game and allows for player faction negotiations. It's also a lot easier to keep the game balanced. If you have too many players if also give you the option of letting then control the "bad guys". Again this worked really well this year in DAK and Dragons as I had player controlled axis and allied factions (4 players each) and a GM controlled "monsters" faction.
3) Playtesting is Overrated But KNOWING the Rules isn't
Some my find this an odd statement but I find deep play testing to be counter-productive. Why? The personality profile of the gamers has a bigger impact on game dynamics and since players choose my game, I can't really control that variable. I do find that when I've play tested too much I've got an almost pre-wired set of assumptions of how the game should play out and can try to direct to achieve that outcome. When I've done this my players have picked it up and become a little frustrated.
While play testing may be overrated, knowing the rules cold isn't and some play testing is required just to make sure you know the rules. If you have to refer to a rule book you've failed. It's really important to be consistent in your application of the rules (except for kids, see below) and some playlets is need to get a handle on the mechanics. It's also useful to help you figure out how to strip down the rules for a con game. Simple is a.ways better.
My infamous (to me) Lundy's Lane game at Fall In in 2012 didn't go that well because I didn't know the rules well enough
4) Set the rules of conduct early and enforce them
Wargamers are an interesting lot. By and large they are a genial group of people but in certain circumstances some individuals can become a pain in the ass (rules lawyers, hyper competitive, whiners). Set out the rules of conduct at the start of the game and enforce them in a genial manner. I do so using self deprecating humor but always make the following points:
- we're all here to have fun
- it's just toy soldiers
- I, as your, GM WILL MAKE MISTAKES
- No vile language / aggressive behavior
In the approximate 500+ gamers I've had at my convention tables I've only had to ask two to leave - one for being so intoxicated he couldn't really speak clearly and the other for wearing a SS-themed T-Shirt that was like a rock band concert tour T-shirt except the concert dates/locales where battles where that SS division fought (and committed atrocities. Free Speech allows that individual to wear the sad shirt, just not at my table.
5) Kids win, always
If you get a young person at your game (under 18) they win - ALWAYS. Sometimes you don't have to intercede as kid luck dice rolling can take over. Other times you may have to -another reason why it's good to have a flexible scenario design). I'm clear to all my players that all of us are playing for second place. The vast majority of players get this and agree. A few don't and I remind them that there are a lot of other games at the con they may enjoy more.
6) Visual Appeal is your best marketing tool:
Having great terrain and mini's is critical to generating interest in your game. If you want players put the effort in to make the game "pop". It's also fun to talk to people in-between games - it's kind of like a grown-ups version of "show and tell" from grade school.
My Games though the years:
"Rome on the March"
Rules Hail Caesar
"A Dacian a Day Keeps the Romans Away"
Rules: Hail Caesar
2012 Fall In
Rules: Ernies home grown rules
War of 1812
"Sink the Tennessee"
Rules: Uncivil Wars
"Prelude to Vicksburg"
Rules: Black Powder
"Sink the Tennessee II"
Rules: Uncivil Wars
"Battle Along the Mississippi"
Rules: Black Powder
"British Intervention in the ACW/Naval "Decision in Delmarva I"
Rules: Sail and Steam Navies
"British Intervention in the ACW/Land Decision in Delmarva 2"
British Intervention in the War of 1812
"Grapeshot on the Chesapeake"
War of 1812
"A Madmans Steeple Chase"
Rules: Musket & Tomahawks
"DAK & Dragons"
"SOCOM & Sorcery"