First things first, guys go to clubs for girls. Girls go to clubs when they find out it’s not just all creepy guys. So get a large Facebook membership base with attractive girls, and attractive high value (none-creepy) guys. This is especially important since these "fans" of your page can be viewed by others. Question is, how do you attract these people? Fake it at first. (At your own discretion) create these fake accounts for the sole purpose of becoming fans of your nightclubs Facebook page.
Once this is done, engage real users by encouraging posts about fun nights and adventures they had at your nightclub. These stories will keep the “Fans” of your page coming back to the page to check for more of these awesome, crazy, unique stories. You can even have contests, for the post which receives the most amount of "Likes" gets a free VIP experience.
Post photos of nights on the Facebook page in different albums titled by dates, which also keeps people coming back for more. Promote this at the club, telling guests to see their photos on your Facebook page! To see these photos, of course, they must be fans of your page, which as we all know all of their friends see, resulting in a viral effect. These photos even allow the people to tag themselves, and reconnect with members of the opposite (or same) sex, through Facebook which they did not have a chance at the nightclub to exchange contact information with. And lastly, post special promotions, nights and deals on the Facebook page.