This one is challenging because it really depends on what type of college student you're looking to target. A question like this is equivalent to asking, I want to target Generation Y - Ok, that's good and dandy but not everyone in Generation Y resonates with the same message or same applications. You first need to identify who it is you're looking to connect with. I don't have that answer because I don't know your product but let's say you're targeting students at a University that are studying Commerce.
For this audience, I'd start by looking at where they spend their time online & offline. University is still a very offline experience and the internet (social media, email, etc) acts as a facilitator for offline experiences and events. Commerce students are likely involved in things like Case Competitions, Guest Speakers, Networking Events and like every other student - Parties. So how would I get them interested in this app? Focus on one of the three simple motivations of a University student - Help them become made, paid or laid.
Made: Facebook penetrated University with an exclusive angle. They started at the prestige universities making people feel as if they "made it" if they were allowed on the site. I can remember people creating second university email accounts just so they could set up an account for their friends. People wanted to feel a part of it and they felt elite by the network starting without letting people in who weren't in college or university.
Paid: Why do students sign up for LinkedIn in their last year? Because they want a job when they graduate. The people on LinkedIn can possibly help them find a job or at least give them an introduction to the right person. Focusing on this story when talking to students was an easy way to onboard a student market in the early days of LinkedIn.
Laid: Tinder and Facebook both did this very well. Let's talk about Tinders approach as it's the most recent story that demonstrated how to do this right. Essentially, their co-founder approached sororities and onboarded their members. From there, she went to fraternities and told them that all of these sorority girls were on the app and they of course, signed up immediately. From there, they held parties at different campuses and invited the most influential people from the various campuses. The word spread, the app spread and success seemed overnight.
So those are the motivations.. Spend some time to dive into the early days of these apps to understand how they grew a bit more. Another app that spread like wildfire in Universities was LikeALittle. It was an app that was focused on the Laid/Made motivation. People wanted to see if they were being talked about (made) and people were trying to flirt with people anonymously (laid) - The growth of that app was magical to watch..
If you want to dive into some actual ideas for your app, give me a ring some time. Happy to help!