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!
4.Have an 30 sec "elevator pitch". hi my name is ____ Im a recent grad interested in XYZ followed by a question i.e. What kinds of candidates are you looking for? What types of positions do you have open etc...
5.Even if they dont have any openings get a business card, send a thank you letter try and write some notes about what you discussed specifically and if things go well, maybe you can even find/add them on LinkedIN.
And of course, dress the part!