Beaker: I don't think you need anything at the meet and greet except maybe an updated resume. I haven't done a meet and greet since they went to it "officially", but the candidate doesn't even have to be at the meet and greet as I understand it. It is certainly helpful if the candidate can make it, but from what I've heard it was more of an interview by the ACP to see how well the sponsor knows the candidate than a "pre" interview of the candidate.
That being said, any contact with the company prior to the interview should be treated as a pre-interview. All of the candidates I have seen around the AOC were in their best suits and looking sharp, but I don't think it is mandatory that they come for the meet and greet. I would do everything I could to be there if I was a candidate however.
It wouldn't hurt to have hard copies of all your paperwork if you do come in for the meet and greet, but I don't think it will be required. Keep updating your online profile (once a month or so) even if you are in the "to be called" stack, they want to see that you have a continued interest in the company. Also make sure you keep the FE written and your Class I medical current.
Good luck.
FJ