I work at Long Island University here in NY. Of the stores I manage on campus, all of the employees are students,which is most likely what your interns will be :).

When working with students, or honestly anyone I've worked with including myself, it's important to assign them work that they actually have an interest in doing; not just going to collect a paycheck. For your particular job you're looking to fill, social media marketing, you'll probably want to reach out to the career services offices within local colleges and universities, and explain that you're looking for students with a strong interest, or major, in marketing. This will narrow your selection of possible interns, but save you the hassle of having someone on staff that is only their to collect a check. Colleges love having partnerships with companies and offering their students resources like jobs and internships, so you shouldn't have a problem making that connection.

When hiring students here, I always let them know that "...if you're here just for the money, it's not worth it. You can find a better paying part-time job elsewhere. If you want to be part of building of something, then you're exactly in the right place." Those are my words of inspiration that SHOCK the students I interview, but they get the point and everyone's happy in the end. You'll end up with people that want to do the work, and love learning beyond the classroom along the way.

I hope this was helpful. I'd love to hop on a call to help you with any further questions on getting those contacts at schools nearby, or any other questions in general. Good luck!