When I ran dance parties for under-18s, I used the rule that people had to hear about the event at least seven times if I really wanted them to turn up.
I would announce the event at a school assembly, but it would be forgotten, so I would stand outside the assembly and hand them a flyer on the way out.
I asked permission to put posters up on the school notice board, tried to get a story in the local newspapers and on radio stations, and put posters in local shopping centres and wherever young people would hang out.
The week before the dance party I stood outside school and handed out flyers (with permission from the school).
One of the most important lessons I have learnt in business is that nobody is thinking of you. You have to remind them constantly of who you are and what you are trying to do.