You should publicize every event you hold on campus. There are many ways to do publicity for your events, and you should make sure you use multiple approaches. The most effective way to publicize an event is to personally invite people you know (inviting them to a Facebook event doesn't count). You should also have a table at a busy intersection on campus. You can meet new people here and give them a personal invitation. Make sure to hand them a flyer to remind them about the event too.
In addition to personal invitations however, you should use Facebook, email blasts, and posters on campus to attract more people. These strategies are not a substitute for personal invitations but they are a useful way to bring in a handful of new people who you wouldn't meet otherwise and to remind people who you have already invited that the event is happening. People are much more likely to come to an event if they see posters all over campus reminding them about it.
We'll be adding more posters here that you can use and customize for your own purposes. For now you can use this all-purpose poster below to publicize general meetings.
Download PDF here or click image below