In my experience there are many things that could attract folks to a fly in: Games and competitions, FAA Wings credit seminars, Aircraft judging, Maintenance and pre-flight competitions, poker runs, guided tours, and local attractions, but the constant seems to be FOOD. To paraphrase an old quote - "If you feed them, they will come".
Another thought, if you are looking to increase local participation consider teaming up with another organization in the area who can attract their own crowd - Sports Car enthusiasts, Motorcycle Nuts, even the Boy Scouts can bring in another whole group of enthusiasts. Local advertising is also important if you want to attract "civilians". Most areas have free 'Service Announcement' sites, handbills, posters, etc can be helpful. Stay away from purchased advertising, though, as it costs more than it produces, usually.
Good luck and remember the PRIME DIRECTIVE ---- HAVE FUN!!