Pre-Prom Photography Tips?

[Kerry.Bush]

Hey all,
I've been following DPS on Twitter and through email but this is my first time using the forums, so bear with me here if I start to act like I don't know what I'm doing. =P
My brother is going to prom tomorrow and I am going to take some pictures of him, his date, and his two friends and their dates prior to dinner at Olive Garden and the dance itself. He told me that he and his friends would be meeting at the house of one of the guys who I don't know, so I don't have a clue of the surroundings I'll be taking the pictures in - though usually this is outside and somewhere around 5 - 6 pm. That I think I can handle. The problem is the posing. I don't have the slightest clue how to pose my brother and his date (who are going as friends and are not, in fact, dating) and the group as a whole. Does anyone have any tips/suggestions/places I could go for help?
Thanks in advance!