Here's the top 20 list of what to do while at Return of the King, courtesy of Bash.org. The sad thing is that I was doing #7 already...
---
For those of you planning on seeing the third LOTR movie at the theater here are some survival tips.

1. Stand up halfway through the movie and yell loudly, "Wait... where the hell is Harry Potter?"

2. Block the entrance to the theater while screaming: "YOU SHALL NOT PASS!" - After the movie, say "Lucas could have done it better."

3. At some point during the movie, stand up and shout: "I must go! Middle Earth needs me!" and run and try to jump into the screen. After bouncing off, return quietly to your seat.

4. Play a drinking game where you have to take a sip every time someone says: "The Ring."

5. Point and laugh whenever someone dies.

6. Ask the nearest ring-nut if he thinks Gandalf went to Hogwarts

7. Finish off every one of Elrond's lines with "Mr. Anderson."

8. When Aragorn is crowned king, stand up and at the top of your lungs sing, "And I did it.... MY way...!"

9. At the end, complain that Gollum was offensive to Ethiopians

10. Talk like Gollum all through the movie. At the end, bite off someone's finger and fall down the stairs.

11. When Shelob appears, pinch the guy in front of you on the back of the neck.

12. Dress up as old ladies and reenact "The Battle of Helms Deep" Monty Python style.

13. When Denethor lights the fire, shout "Barbecue!"

14. Ask people around you who they think is the next "Terminator" sent from the Middle Earth of the future to assassinate Frodo Baggins

15. In TTT when the Ents decide to march to war, stand up and shout "RUN FOREST, RUN!"

16. Every time someone kills an Orc, yell: "That's what I'm Tolkien about!" See how long it takes before you get
kicked out of the theatre.

17. During a wide shot of a battle, inquire, "Where's Waldo?"

18. Talk loudly about how you heard that there is a single frame of a nude Elf hidden somewhere in the movie.

19. Start an Orc sing-a-long.

20. Come to the premiere dressed as Frankenfurter and wander around looking terribly confused.