Partner with an organization or business from outside of your church. Could be a local ymca or athletic club. These organizations already have an audience of people that will come to events they sponsor. By partnering, you nearly have guaranteed people at your event and you are including a group of people that may never step foot on your campus. You are showing support of this organization, and your community notices this. Your event is more likely to be a success, and will take away people's expectations of a lame church event.