“They’re already here.”

Though it’s seven months away from hitting theaters, “War of the Worlds” already has a respectable marketing foundation thanks to that solid tagline, which recalls the “They’re here” tagline for “Poltergeist.”

“We think ‘They’re already here’ is perfectly evocative,” notes Paramount vice chair Rob Friedman. “It makes people go, ‘Wow, I know what this is about and I want to go see it.’ It’s the first step in building awareness.”

Veteran publicist Marvin Levy notes the tagline is something of a bookend to “We are not alone,” the catchphrase of another Spielberg sci-fier, “Close Encounters of the Third Kind.”

Other high-profile 2005 releases have taglines ready: “XXX: State of the Union” (“Prepare for the next level”), “Hitch” (“The cure for the common man”), “The Longest Yard” (“It was hard to put a team together until they found out who they were playing”), “The Weatherman” (“Bring your umbrella”) and “Be Cool” (“Everybody is looking for the next big hit”).

Taglines — those soundbite summations of films — are tricky turf in Hollywood. Many are either obscure or forgettable to the point that plenty of films (“Sideways,” “The Polar Express”) don’t use them at all.”

But a few have managed to be memorable, with marketing mavens usually placing Steve Frankfort’s “In space, no one can hear you scream” tagline for “Alien” at the top of the list.

“The ‘Alien’ tagline was sheer genius because it created the kind of buzz you can’t buy,” one vet asserts. “But it’s like lightning in a bottle.”

Some of the other greats: “Pray for Rosemary’s baby” (“Rosemary’s Baby”); “Where were you in ’62?” (“American Graffiti”); “Protecting the earth from the scum of the universe” (“Men in Black”); “The snobs against the slobs” (“Caddyshack”); “They’re young, they’re in love and they kill people” (“Bonnie and Clyde”); “You’ll believe a man can fly” (“Superman”); “Be afraid, be very afraid” (“The Fly”); “Houston, we have a problem” (“Apollo 13”); and “Just when you thought it was safe to go back in the water…” (“Jaws 2”).

In earlier times, when moviegoing was the nation’s major entertainment, taglines tended toward the breathless hard sell: “The Monster demands a mate” (“Bride of Frankenstein”); “It was murder from the moment they met” (“Double Indemnity”); “Only the rainbow can duplicate its brilliance” (“The Adventures of Robin Hood”); “Everybody’s talking about it! It’s terrific!” (“Citizen Kane”); or “Three wonderful loves in the best picture of the year” (“The Best Years of Our Lives”).

Levy recalls one of the era’s most memorable taglines was spun in 1945 for “Adventure,” marking the return of Clark Gable from the military into a movie pairing with Greer Garson: “Gable’s back and Garson’s got him!”

But with Hollywood reinventing itself in the ’60s, the sledgehammer approach stopped being viable, and marketers found themselves opting for subtlety and irony such as “The Graduate’s” “This is Benjamin. He’s a little worried about his future” and “Not that it matters, but most of it is true” for “Butch Cassidy and the Sundance Kid.”

“With the market becoming increasingly fragmented, you can’t really aim wide anymore on every film,” asserts veteran publicist Henri Bollinger. “You have to hit your target audience or they won’t come see your movie.”

For example, “The Incredibles” used half a dozen taglines — “Save the day,” “On November 5, expect the Incredible,” “Twice the hero he used to be,” “Sock ‘er Mom,” “Super cool,” “No gut, no glory” –aimed at specific audience segments. “I thought ‘no gut, no glory’ was especially effective at bringing in adults,” one marketing vet notes.

Sometimes a single word can be huge, such as on “Life Is Beautiful,” which was dubbed “an unforgettable fable,” defusing much of the controversy over it being set in a concentration camp.

It’s not as if having a great tagline is crucial, by the way. “Titanic,” the most successful film of all time, had a relatively mundane one — “Nothing on earth could come between them” — but marketers agree it did the job of underscoring the love story and attracting female patrons.

The “Whoever wins, we lose” tagline is cited as one of the best recent examples of connecting with a pic’s most likely aud, in this case for “Alien vs. Predator.” High marks also went to “Bridget Jones: The Edge of Reason” for “Big lawyer, big liar, big dilemma” and to “Lemony Snicket’s A Series of Unfortunate Events” for “Mishaps. Misadventures. Mayhem. Oh Joy” for nailing the tone of Daniel Handler’s books.

By contrast, several marketers were perplexed by the seeming over-reach of the tagline “In the era of cool, he was the soundtrack” for “Beyond the Sea.”

Typically, studios hire ad copywriters, opting for the same people who come up with titles, and either show them a rough cut or give them the script. Pay for the work is in the $25,000-$50,000 range plus a bonus if the tagline’s used.

But almost anyone — studios execs, the writers, the producers — can author the tagline.

Ron Parker, a producer on “My Stepmother Is an Alien,” recalls that his tagline (“He married a girl from out of town … way out of town”) remained on the romantic comedy even as it went through four studios in development.

“It really is the right tagline, because I still wanted to emphasize that the movie was about the romance, even though the title didn’t really reflect that,” Parker recalls.