1. Research and look at the companies in advance. Use the map layout, predict which will have longer lines. Also research positions they are looking for at the fair and even check their online site, there may be something on there that you can say "I also saw on your career site...this position is it still avail.".The recruiter might say "oh,im not sure let me forward your resume to XYZ"If they say that follow up with them!
2. Be yourself (easier said than done) - Be personable and energetic! Don't be intimated by what other people are doing. You'll see plenty of monotone,serious people. Don't be like them! You need recruiters to remember you! So smile often (but not too often you don't want seem like a creeper! )
3. Have plenty of resumes and a folder or pockets to collect business cards!