When my friends and I went to see HBP, we got there at 9 pm for a 12 am show. We got to sit in the first row because all nine theaters that were playing it filled up that early.
For New Moon, I think it will be a bit calmer, but I'm thinking my friend's plan to split up (We have a group of six) while half wait in line and the others get dinner isn't a bad idea.
And that is a great idea for theaters to play a double feature of both Twilight and then show New Moon. Yes, I would take a nap, Ellie!