First, and Most Importantly, have fun with your event! If your description is dry, people will assume your organization is boring. Get people excited about attending, let them see why you're so happy to do what you do as a brother!
Unless there is a specific reason not to, leave all the default settings the way they are. In other words, allow guests to invite others, upload photos, write on the wall, etc. unless there is a very specific reason that this particular event should have additional privacy setting enabled. The reason is that every one of these activities creates news items that go out into the feeds of those individuals and their friends. This is great viral visibility for you and for them. Here is an example of all options you want to check:
Be sure to choose a really catchy title, subtitle and photo. These three fields are the only ones seen in requests when you invite your friends (and they invite their friends). The small greeting you can include goes out in the email notification, so thats important too.
Make sure to choose an engaging photo for your main event description and add multiple photos related to the event to pique interest. An engaging photo should be eye-catching, warm, friendly, and inviting. Typically a persons face is better than logos/images/graphics. You MUST include a photo or your event will have that nasty question mark. And who wants to attend a ? event?
Spread the word. Click the "Share" button and post to your profile and your invite will go on your wall for all to see. Or use the "Share" button to send an invite to specific friends or lists.
Got Twitter? Send out tweets with a link to the Facebook event. Preferably not just, "Check out my event! [insert link]." Rather, offer something enticing like, "Learn How to Create a BUZZ With Facebook Events [insert link, use a short URL]". (Link to either the Facebook event page or your registration page.) Also include the link in your Facebook status updates periodically and mention your event on Plurk, LinkedIn, Plaxo, FriendFeed, and/or Ping.fm - whichever platforms you're active on and have followers/friends on! Your friends and followers will happily pass the snipped link on for you.