If they are bored that means you dont have enough content and also that you are not getting them involved in posting content.
Leave a token at 5 local nightclubs and let the bartenders know the deal. Then tell your users that one that collects all the tokens correctly gets something (gift certificate or something). Maybe to get a token they have to answer a question or write something on the site (article or something), up to you how you run it.
Remember its not about rules or any of that stuff, its about content, regarless what a site looks like or functions if the right content is there that they want then they will join and many will participate. Content is the key always...
You might get something from this.. https://developers.oxwall.com/forum/topic/51775
But as i said not knowing what your site is about, dating, social, whatever its hard for me to give advice because there are a kazillion variables. But basically ask yourself as a user/consumer "why do i create content on websites" what makes you post on websites usually works for others as well.