Bring a portfolio or folder with multiple copies of your resume and something to carry information and goodies you pick up at the fair. Research the participating companies. Research the positions available. Put together your business attire. Expect to see a large area filled with table after table and row after row of companies with large displays, freebies, and a lot of information.
Long lines are also a possibility.
Tell me about yourself. Tell me a time when someone in your group wasn't doing their part of a project in a timely manner and how did you handle that situation. See your career center for more examples of interview questions.