We have held two events so far, and plan putting on at least four more. In my experience, some will help out for free, others will need the incentive of pay. Whatever way, you need a small army of people to put on an event. Let people you know you're putting on an event. Tell everyone and anyone.
Friends bring friends.
Its the best form of advertising. It got me pumped up to put on the best event I could. For the advertisement we tried to be as creative as possible. We ordered 3D-hologram stickers from Fantasma, Il. and got an artist friend to design the flyer. We advertised for about a week before the event, but that was because it was on-campus, so not much more time was needed.