You do have the option to move to another table and plan to come back later. If you discover a real interest in an employer, find out the procedures required to secure an interview. Show enthusiasm, but don't go for the hard-sell approach. At some career fairs, initial screening interviews may be done on the spot. Other times, the career fair is used to pre-screen applicants for interviews to be conducted later.
Sincerity always wins.
Don't lay it on too thick. Try to get your resume into a person's hands and at least say a few words. Don't just drop your resume on the display table. I'm very interested in talking to you. Look around the display for the recruiter's business card and get some literature with the company's address.