What should I expect at a VersaEmerge meet and greet or any meet and greet in general.?

I just got two meet and greet passes to meet VersaEmerge at their first stop of their Vultures Unite Tour in Dallas. I've met plenty of bands before, I've just never had a meet&greet pass. So I'm not too sure on how everything works. I know that every band and venue are different, but can someone please kinda give me an idea of what it's like.? And if you've met VE before, what are they like.? What should I bring to have them sign.? There's gonna be 25 of us so how much time do you think I'll actually have to talk to them one on one.? I'm not a complete idiot and I know not to freak out or drool over Sierra, but I just wanna know what it's usually like. Also, I was planning on wearing my 'Where the F*ck is Sierra' shirt I got from Warped Tour before I found out about the meet and greet. Now I'm not too sure if I should wear it since I'm gonna be meeting her and all. I think it might be a little akward to have her on my chest when I'm talking to her. Any suggestions on what to wear T-shirt wise.? Also, any advice/tips would be great too. Thanks in advance.