Basically, what it is.... they have two separate lines- one for people who bought dining packages and one for standby people. They let the dining package people in first (massive line in it itself, and I'd probably hop in the at least an early early for this too if you care to have a better seat as seating is a free for all, if you show up last minute... you'll get in, but you'll probably be off to the sides/back) and then once they've all seated in, they let as many standby people in as they can. Of course, they make announcements for dining package people to scrunch together/move to ends of rows to accommodate as many people as possible (and many of them will grumble, and not budge saying "I paid for this!").
As someone said- plan on being in that line several hours early, and even then nothing is guaranteed. Good Luck.