I'll echo what everyone else says: dress comfortably and warmly, go as early as you can stand to prior to 7 AM to queue up, bring snacks, sammies, drinks, whatever and change for the vending machines if you run out. Definitely bring a good book or two and anything else you don't mind doing for hours on end (knitting, crocheting, crossword puzzles, etc). And don't forget all your paperwork and your passport.

I would also warn against line jumpers as well. When we went, there was a young lady who tried to jump in front of us and several other people. I wasn't having it and neither were some other folks. Just a word of caution.
Hope it goes well!!!!