I have been a GM of tabletop games for over ten years, a participant in live action games for
almost as long and a game-master of same since 1995. My GMing credits include
two long-term Vampire LARPs and the Cthulhu LARP troupes Serious Moonlight and
Chuckling Cthulhu. So how's that for qualifications? :-)
If you are looking for more in-depth advice than the
common-sense stuff I'm covering here, I suggest you check out my other
LARP advice.
General Rules
Always take your time in preparation. Your players won't die if they have to wait an extra while and the fewer decisions you have to make on the fly, the more smoothly things will run. When in doubt, tell the player you'll get back to them and make good on that promise.
Benefit from those who have gone before; ask advice from other LARP game-masters.
Communication is also essential. Use all the tools you can - telephone, the postal service and e-mail.
Addendum to the above: encourage your players to be honest in their relations with you - and, if needed, remind them of the difference between being honest and being insulting.
Players will do practically anything for experience points. Use this to your advantage.
But never give XP to keep them 'happy'.
A web page is cool, but not essential. If someone volunteers to make one, ask for a portfolio of other websites they have built before deciding. If you have a web page, take the time to link to as many related sites as possible, as that may garner you new players.
It is not a sin to delegate duties. In fact, it's essential. There is no such thing as 'too many assistants'
Your assistants are volunteers and thus deserve more slack in terms of deadlines and quality than a paid professional would receive, so don't push them as hard as you would a paid service. However, if a volunteer is making constant mistakes and degrading the quality of the game, let them go as soon as possible.
The point of this is to have fun. If you're not having fun, you're players won't, either. But try to keep your temper, okay?
Before You Announce The Game
Take your time deciding on your mythos, setting and character needs. Wait until you are ready to answer your players' questions. Once you announce the game, you will be swamped by inquiries and may not have the time to make a cool, well-reasoned decision.
Decide upon your game mechanic and establish how you wish to keep track of the players' characters- and assemble it before you accept any concepts from your players.
Decide what structure fits you. Do you want to have a pre-game meeting a few days before where players can spend their experience points and ask questions? I find that useful for a large, high-maintainance group. If yours is a weekly game, a newsletter is pointless, but a newsgroup or listserv might prove useful.
Announcing The Game
Word of mouth is well and good, but use all options open to you.
Get the word out to local gaming and comic book stores, gaming conventions and other larps in the area by distributing fliers or e-mail. Some stores will only take 3x5 cards for announcements, so take the time to create a neat, printed card. It will attract more attention and be easier to read than a hand-scrawled announcement.
Check out Yahoo Groups or the Usenet for groups/lists where you can spread
the word about your event.
Don't forget to include all contact information on your publicity, and any special conditions of the game that might affect a player's decision
(such as game locale, age restrictions, etc)
Running the Game
Take the amount of preparation time you have budgeted and double it. I'm not kidding. Having your prep done ahead of time is much more relaxing than arriving to the game with things "almost done".
Estimate the amount of supplies you will need - from cards, to stickers, to bits of string - and double it.
Arrive at your game site as early as possible, with as many helpers as you can muster.
Ensure your players understand the purpose of your assistants and use them. The chief game-master should not be making every decision, nor even the majority of them.
If your game-mechanic is particularly obscure or difficult, you may want to consider running a "Newbie School" prior to game-time. If your system is both obscure and difficult, ditch it.
Have a sign-in sheet or other method to get the current contact information for every player at every game. In my experience, I find that creating an 'experience sheet' at the end of the game works well. If the player doesn't fill it out, then they don't get any experience. Unsurprisingly, there's about a 98% return rate on Experience Sheets.
If you are sick or the real world is demanding your time, let someone else run the game or cancel the event! Nobody loves a masochist, and you'll be angry at the game for obstructing your life.
Encourage your players to bring food and drink to share. Hungry gamers are cranky and unhappy gamers. Ditto for the GM.
After the Game
Try to take a day to relax, before you jump into the grind again. Take the phone off the hook, turn off the computer, or just go out of town for a while. You deserve time off.
Once you've recovered, get a newsletter or post-game e-mail out as soon as possible. This is part of the 'communication is essential' rule.
Meet with your assistants and dissect the game. Find problems and solve them as quickly as possible. This includes plot problems, logistics problems and player issues.
As Time Passes
As your game progresses, encourage your players to develop their characters (see How To Play In A LARP for ideas) and then reward them for doing so, and try your best to integrate that into your chronicle.
Understand that, even while you encourage your players to develop their characters, you cannot give your LARP players the same degree of individual attention that they would receive in a tabletop
game - and make this fact clear to your players. If you try to give 20+
players individualized attention, you will go nuts and nothing else will get done, either.
Create specialized positions as needed - such as a props-master, or a
reviewer-of-character-backgrounds.
Don't be afraid to make changes - to your logistics, your game system, your game's mythos, anything. If it's good for the game and for you, then do it. Of course, be wary of changing things just for the sake of change. All the LARP GMs (myself included) have made the mistake of trying to re-invent the wheel. This is frustrating and time-wasting, avoid it if you can.