Here are the basics of how I run the Albany gameday:
1. Finding a date that works for you and your location. Keep in mind you will have to compete with things like Larkfest and Tulipfest. I'm willing to help you set up a date. George is very laid back and usually likes to be around when we are there so it shouldn't be too hard.
2. People. Getting people to show up usually isn't a problem. Where we tend to run into a problem is we're always short DMs. For every 5-6 people you need one DM. We can usually fill 3 slots in the morning and 3-4 in the afternoon. Of course, every time we do it things change more people show up, people don't show up, or we get a DM who is willing to take 7 or more players (bless them).
3. Advertising. ENwrold has treated us well. Unlike Boston, the Albany, NY population on ENworld is a bit lacking. I tend to start a tread on Zombie Planet's boards, sometimes on rpg.net, print a flyer for Zombie Planet's cork board and put flyers in comic shops and any place that people who might be interested would see.
4. Getting people to show up. Life always gets in the way. A good percent of people who say they might make it don't, a small part of players the sign up might not show up, and some have flaked in the past leaving players in the lurch. When I'm not running two games, I try to keep a small game I could run on hand in case a DM drops out.
5. The Games. I always have to beg, borrow, steal, plead, and blackmail to get DMs. Sometimes enough people that want to run fall into my lap but I usually have to give some people a nudge that say "I'd like to run X someday". A gameday is a great place to run something you would never get to run otherwise.
6. Communication. I tend to keep two lists of games and players. This is basically for the people that aren't on ENworld. Since some people aren't into message boards and don't seem to 'get' them.
7. Food. I always lose money on the food. It's gotten to the point where we go through two 24 cut pizzas easy. Last time I ordered 3 24s and that seemed to be too much. At different times I've been a few dollars short of getting all the money I put into the food back and at others I've been a good $20+ into the red.
The way I do things isn't the only way to organize a gameday so your mileage may very. It has gotten easier with each event I do but every six months can at times feel like not enough down time. The spring has always brought in less people so I though it would be a good time for a 'vacation'.