Ahh, LanParties. Successful LanParties always involve the following, in large quantities:
Ok, so far this probably just sounds like your typical frat party, except maybe for the computers and the caffeine. What's so special about LanParties? Basically you get a bunch of people and their computers together, and you play network computer games. LanParties must last for greater than 24 hours. That's typically why you order twice as much pizza as you think you'll need; you'll be hungry again after another 12 hours!
I've hosted a bunch of LanParties, in Calgary, at my parents' place. Bless their hearts for putting up with it! We'd often have 6 people in the basement, with their computers, drinking and laughing and eating pizza until all hours. Ah.. the good 'ole days. Those kinds of LanParties are probably a lot more common than you might think. I think a lot of kids in HighSchool? are having these sorts of small LanParties these days.
I've also been to bigger, professionally organised LanParties. There's something to be said for both. At the smaller ones, you typically know the people better and it's easier to get everybody into one game together, but at the bigger ones, there are more people, bigger games, tournaments, and you can meet new people.
Finally, you might ask, what's the point of all this? Can't you just play on the Internet? Yeah, but at LanParties the network (being local) will have very low latency, which makes gaming much more enjoyable. Also, when you discover that it was ph34rmonk3y who just killed you, you can stand up and scream some (preferably extremely profane) insult at her. And yes, girls do go to LanParties, sometimes. And often, they beat the living crap outta me!