Have a sip every time:

There's a personality switch between Smeagol and Gollum.

Aragorn 'vibes' with someone not Arwen.

Someone says, "that didn't happen in the book!"

Gandalf shows up in a blast of blinding white light.

Frodo wigs out.

Merry's cut changes sides on his forehead.

There's a flashback featuring Arwen.

A tree speaks.

Gimli is the butt of a joke.

There's a conversation held in Elvish.

Faramir displays the bullying characteristics of Boromir but without the charm.

Aragorn uses his tracking skills.

Legolas gets fatalistic.

Arwen acts like a love sick teenager and needs to be chastised by Elrond.

Sam displays even more codependency as Frodo pulls away.

Legolas quotes some pithy elf saying.

Someone (or thing) gets thrown off of a high spot.

The balcony scene at Isengard evokes memories of Evita.

The need for formal introductions seems to have passed.

Eowyn *wants* to be a sword fighting, orc-killing tom boy but Uncle Theoden just won't let her.

What's left of the Fellowship seems to bring bad news and destruction no matter where they go.

Eowyn, honey, your zipper is showing.

An Ent goes Huuummmmmmmm...

Every time we see footage that was used in FotR.

Two sips every time:

"Toss me."

Legolas mounts a horse in an unorthodox manner.

A shield is used as a surfboard.

An Uruk-Hai is born.

Being dunked in a river still doesn't manage to wash Aragorn clean.

An elf is killed in slow motion accompanied by plaintive singing.

A horse kisses Aragorn.

Sam starts to feel inferior to Gollum.

Gandalf acts holier than thou.

A ladder goes up.

Aragorn takes a flying leap off a cliff.

An entire battalion of elves show up out of nowhere.

Sam is referred to as a fat hobbit.

Aragorn stubs his toe on an orc helmet.

Someone refers to Wormtongue as Brain Guy. (OK, that's just for me)

The Calvary shows up.

You can see through Arwen's purple toga.

Pippin outsmarts Treebeard.

Having Saruman forcibly ejected from Theoden's body shows a marked improvement in his skin condition.

Gandalf's new and improved powers don't work unless he takes the gray cloak off.

Aragorn lounges around Rivendale like he owns the place.

No matter what the Elf stays Tide clean.

Legolas stands up for Gimli.

The ickiness that is Wormtongue gives you the willies.

The Swagger (tm).

A reference to hobbits as fresh meat is made.

A Ringwraith shows up but it's not scary.

Merry and Pippin hitch a ride with an Ent.

Elves have to face the same direction as their leader with whiplash inducing speed.

Frodo takes a dip in the Dead Marsh.

You start to think that Elrond really can't stand Aragorn touching his daughter.

Gandalf acts like an old Jewish grandma to keep his staff. Oy, my back...

Three sips every time:

Galadriel has a voice over.

Smeagol sings.

A ladder falls down. Take another drink if Legolas's brilliant marksmanship causes it.

Someone points at locations on a map despite the area being well within known territory to all concerned and the towns are clearly labeled in dark, easy to read ink.

Helm's Deep is under siege by 10,000 orcs yet Aragorn and Gimli sneak out an unlocked side entrance conveniently placed ten feet away from the front door. -Have an extra drink when you realize Wormtongue would have known about it.

There's a mass exodus.

Frodo and Sam are at the Black Gate, the troops are marching in but you can't help but sing the guards' marching chant from the Wizard of Oz.

Hey look! There's that ring this is all about.

Sure there's 10,000 of them but clustering together like that is tactically stupid.

Whole bottle when:

Almost drowning in a river doesn't do it, being soaked in freezing water doesn't do it, being washed ashore on very sharp rocks doesn't do it, the raging headache you know he must have doesn't do it, getting snogged by a big stinky horse doesn't do it; but, the nightmare of Arwen wakes Aragorn up like a flash.