Get a solid game plan
So you want to run an event, right? Well, before you go shooting your mouth off, Eventy McRunnerson, you need to get a gameplan set down.
Ask yourself what exactly you want to accomplish in your event. Do you want to hold some sort of contest? Are you running some sort of talent show, or poetry contest? Are you assembling some of the best and brightest in your guild for a structured RP event? All of these events have very different goals and very different target audiences. They all require different amounts of manpower, and different lengths of time for preparation.
"Sure, maybe you don't need others to help you organize a simple concert schedule, but wouldn't it be nice to have a few people on the main road, pointing others to your concert so they don't get lost along the way?"
During these planning phases, scout out where you want to hold your event. It should be some place in the game that you're familiar with, as you may need to provide instructions on where to meet, and it should be somewhere away from people. You don't want to disturb others, nor would you like to have your event disturbed. (Unless, of course, your event requires you to be in the thick of things.)
Lastly, if your event requires an in-game reward, get that reward before you go any further. It's not very good when you advertise that you'll be giving away 1,000,000 gold, but only have 100 in your pocket!
It's dangerous to go alone
Having others help you plan and run the event is always helpful, even if you think you can go it alone. Sure, maybe you don't need others to help you organize a simple concert schedule, but wouldn't it be nice to have a few people on the main road, pointing others to your concert so they don't get lost along the way?
Get a few of your friends to help you plan your event, or rally together a few of your guildmates. When you're setting things up, they might notice things you didn't, they might have some helpful advice, and they can certainly help organize the chaos that your live event will undoubtedly become.
When event time rolls around, also make sure you have a good method of communication with the people who are helping you run the event. Either form a party, hijack guild chat, make a chat room (if your game supports that), or jump into the same ventrilo channel. When everyone running the event is on the same page, everything will run smoothly.