This is part of the make your own guide to creating role playing systems.
One of the things that most people don't understand is the sheer number of ways to play games. Most GMs are stuck in a mindset: "Six guys sitting around a table, marking papers and rolling dice, once per week."
Well, that's certainly not the only way to play. In fact, it isn't even the best.
What sitting at a table together on a schedule gives you, primarily, is focus. It's really easy to play the game if everyone gets together on a specific night, at a specific time. And if Jimmy doesn't show, play without him. Even then, however, there are other methods. :P
How you want your game to run is a big choice. Most GMs will probably think in terms of "once per week" or some such. If that's your first instinct, then you can't pick that. It's much better to run anything else - one-shots, if your time is strict. There's nothing inherently wrong with once-a-week (or twice-a-month) games, but there's also nothing inherently wrong with sauerkraut. We still eat other things.
Here are some of my favorite schedules (This doesn't even take into account how the game is played, which is really important, too. So many factors!):
Once a week.
Super common. Generally about how often people think they want to play. Not long enough to completely forget about how much fun you had (or didn't have), although a lot of the vigor will wear off, especially among players who don't work 40 hours a week.
Once per (two weeks/one month).
A lot of people that have lives prefer this length of time. "I can make it every other Saturday..."
This won't be often enough to keep up with students or the unemployed, but for people who work too hard, it's probably ideal. However, I would suggest that you limit yourself to only people who work too hard if you choose this method: the odd one out tends to be really the odd one out.
Two+ per week.
It's very uncommon for one team to run the same game twice per week. I guess there's a feeling that you're basically spending your life on this game. The upside is that the energy level will remain high (presuming it's a fun game). The downside is that nobody will want to sign up. The only time I've been able to run like this is with my room-mates back in college.
This is, however, a really great way to level up your GMing skills. It's like weight-training for geeks.
Specifically, the one-shot that lasts as long as one session normally would.
One-shots are occasionally perfect for what you need. However, many games (and systems) are rigged for long-term fun rather than short-term fun, and you'll never feel that pull with one-shots.
Still, it's really easy to get people signed up for one-shots. :)
At some point or another, every GM dreams of running two parties in the same universe, typically each party running once per week. You might have even heard stories. I'm here to tell you: Don't do it!
The only way to successfully run a multi-party game is to be an expert at front-loading your metagames. Yeah, didn't think so. Try some other situations with heavy metagaming, work your way up to this.
A one-shot which lasts eight or more hours, often stretching into days. This isn't actually as uncommon as it sounds: Diplomacy is a long-ass one-shot, and people play that basically every weekend.
A LAOS isn't really suitable for sit-in-a-circle-and-roll-dice games. There needs to be a structure that allows players to sift in and out as food, bathroom, and sleep beckon. And showers. So, typically, these games are LARPs.
The upside to these is that immersion is fantastically strong, which is more important than you might think. The downside is that you have to be completely insane to sign up for such a game. To say nothing of how much pain it inflicts on the GMs.
The churner is a game which operates on the player's time. An example would be assassins.
Churners are difficult to balance, because players all have radically different amounts of time to throw at playing the game. This is a very difficult kind of game to run properly, although everyone should try to run one.
This is a reoccurring game, typically a tabletop or LARP, in which the time between sessions still has game-related stuff in it. An example would be a tabletop with individual mini-sessions. Another example would be a game where you throw so much information at the players that they have to spend all week trying to sift through it.
These games tend to be very big on the metagaming, so if you want to hone your meta-skills, this would be a good way to run. Remember, though: "normal" systems aren't suited. They're all designed for simultaneous play rather than asynchronous play. You see the tear lines pretty quick.
Done right, however, this completely negates the way that players lose interest between sessions. Used correctly, players will come into the room half an hour early, waving papers at you and yelling over each other.
At the Con.
Some games you'll want to run at a weekend-long convention of some sort. Typically a 4-6 hour block of time. Something to keep in mind, regardless of what kind of game it is, is that all your players will be tired. Yeah, best to take that under consideration.
Also take into consideration who your competitors are. In the beginning, I screwed up by running opposite the Big Bad Game. As time went on, I watched other people make the same mistake. Just because Saturday at 7 PM is best for you doesn't mean it's the best time to run your game.
After all, I might be running my game then... ;D