Once you have your on-campus interview scheduled, be sure to prepare properly for the interview by knowing everything you possibly can about the employer. Nothing turns me off quicker than a student who has no idea what my company does. And nothing will more quickly impress me than a student who has fully researched my company. Do your homework. Read Section 3, Interviewing Success and especially Chapter 18, On-Campus Interviewing Success.
Also, keep in mind that you should not depend exclusively on interviewing on campus to guarantee after-graduation employment. There are far more employers than just those that are visiting your campus. Many of the best employers may not be visiting your campus. So make sure to take note of the chapters on how to reach out to these "other" employers.