What can I do to stand out at a job fair?
Print plenty of resumes.
This should be a given for a job fair, but the same thing applies to second-round interviews. You never know if multiple people would be interested in your qualifications.
Tip: Handing out business cards in addition to a resume is becoming more popular, even among college students looking for internships. It cannot hurt to make sure that the person who is hiring has another way of contacting you.