Saw this on another message board. Personal favorites are bolded
Stand up halfway through the movie and yell loudly, "Wait... where the hell is Harry Potter?"
Block the entrance to the theater while screaming: "YOU SHALL NOT PASS!"
After the movie, say "Lucas could have done it better."
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.
Play a drinking game where you have to take a sip every time someone says: "The Ring."
Point and laugh whenever someone dies.
Ask the nearest ring-nut if he thinks Gandalf went to Hogwarts, and if so, what house do you think he was in.
Finish off every one of Elrond's lines with "Mr. Anderson."
When Aragorn is crowned king, stand up and at the top of your lungs sing, "And I did it.... MY way...!"
At the end, complain that Gollum was offensive to Ethiopians. -Talk like Gollum all through the movie. At the end, bite off someone's finger and fall down the stairs.
When Shelob appears, pinch the guy in front of you on the back of the neck.
Dress up as old ladies and reenact "The Battle of Helms Deep" Monty Python style.
When Denethor lights the fire, shout "Barbecue!"
Ask people around you who they think is the next "Terminator" sent from the Middle Earth of the future to assassinate Frodo Baggins.
In The Two Towers when the Ents decide to march to war, stand up and shout "RUN FOREST, RUN!"
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.)
During a wide shot of a battle, inquire, "Where's Waldo?"
Talk loudly about how you heard that there is a single frame of a nude Elf hidden somewhere in the movie.
Start an Orc sing-a-long.
Come to the premiere dressed as Frankenfurter and wander around looking terribly confused.
When they go in the paths of the dead, wait for tense moment and shout, "I see dead people!"
Imitate what you think a conversation between Gollum, Dobby and Yoda would be like.
Release a jar of daddy-long-legs into the theater during the Shelob scene.
Wonder out loud if Aragorn is going to run for governor of California.
When Sam holds Frodo's hand (or otherwise), start singing, "The Ambiguously Gay Duo!"
When Shelob comes on, exclaim, "Man! Charlotte's really let herself go!"
Give the orcs a loud internal monologue ..
"I swear that mountain troll checked me out... n'ah ... HEY he did it again."
"This is a big day for me, first I was promoted to the front of the charge, and my wife is pregnant ... and I won the lottery ... hey what's this arrow doing in me?"
"It's Gandalf! HEY MAN I went to highschool with you! How about we *Gandalf makes some magic* ... That's weak sauce G-man."
Every time you see any form of Sauron on screen yell out
"Sauron ... digivolve to ... SARUMAN!"
Yell out "Where's the hell is the pirate ship? This remake of the Goonies is retarded."
Every time someone mentions the horrors of the ring yell out "I got yer ring right HERE" and grasp yourself accordingly.
Whenever there is a wide shot of elves shout "Santa's gonna get middle earth on your ass!"
Every time an orc passes the screen nudge a stranger next to you and whisper "Done her."
For every shot of Legolas and Gimli together shout out an appropriate Jay and Silent Bob quote.
When the ring is destoryed shout out "OHhhhh ... THAT was the one ring ... I get it!"
Whenever Legolas is on screen continually mumble "Damn she's fine."
At Gandalf's huge entrance to the Helms Deep battle sing "The hills are alive with the sound of music." The higher pitched the better.