You'd think that Western Civilization, with all its rules for romance, could tell us just once what to do when romance bows out.

The truth of the matter, where love's concerned, is that beginnings are easy, and endings are a very bad business. Whither Rhett Butler? Gone with the wind. Now all we have is Woody Allen: "A relationship is like a shark.It has to keep moving forward or it dies. What we have on our hands is a dead shark."

As Valentine's Day draws nigh, and maybe we're feeling a bit fragile, we might do worse than consider some guidelines for breaking up. We've all been through it, more times than most of us care to recall, but we seldom get it right. What to do? Where to go? What to wear? Such questions deserve more than Top Forty tunes.

As for beginnings, history and convention have dealt us an embarrassment of riches: long-stemmed roses, candlelit suppers followed by moonlit walks; reference books as various as The Art of Courtly Love (16th-century Italy) and How to Pick up Girls (20th-century America); waterbeds, mirrors; we needn't go into the rest.

Endings, though, are rich mostly in embarrassments: guilt, shame, the pang of regret: inevitable fruits of bungling. Take the local painter who unwittingly surprised his girlfriend with a new nude above the headboard; the ensuing scene was not a pretty sight. Indeed, most breakups take on a chaotic life of their own.

"I'm the typical American woman -- five feet tall . . . freckles . . . 25 . . . smart," says J, a Westerner turned Washingtonian. "I'm a normal person, really. Last June, when I left my job for a better one, there was a going away party and my boyfriend came. He thought I acted 'obnoxious,' or that's what he told me the next week, when he started screaming at me like a madman. So I ended it.

"We got back together in August for my birthday, and went out again for the next two months, at the end of which he said, 'I really felt, J, that sex was unimportant to me until -- (I thought he was going to say, 'until you came along') -- until I had group sex with K and three other girls at Tyson's Corner.' That was our second breakup.

"A couple of days later, he called up, very apologetic. 'Well,' I told him, 'go see a psychiatrist, call me every two days, take aspirin, and if you do this for two weeks, I'll go out with you again.' We did, until the middle of December, when he told me he'd started dating someone else that he'd met in a 'weird way.' That was our third breakup. A couple of weeks later, he called up again with, 'I really miss you, I think you're wonderful, I'm sorry about everything, we have to get together.' So I thought, if he was willing to change, I could give him another chance. We went out the following Friday and had a wonderful time.

"Two days laters, he proved himself wrong. He flew into a rampage and called me a 'creep' in front of other people. So we broke up for the last time, traveling from one New Year's party to another on the Beltway. The final phase came just last week. A friend was giving a party and called to ask if she could invite So-and-so and 'how would you feel about it?' I said, 'Fine, you can still have the party, but I will personally do something to his body.'" (If some of this seems too painful, let's for the moment be brave.)

Washington, happily, is a place that fairly teems with ways and means to maneuver your affair, relationship, whatever, to a satisfactory conclusion. The geography (three perfectly nice airports, a cavernous train station, countless marble crags, a hundred tricky hallways) is unsurpassed. The ambiance of some locales might have been ready-made for the purpose.

The Rosslyn Metro stop, for instance, is nonpareil for staging The Easy Letdown, a type of breakup noted for shameless wishy-washyness or simple cowardice. Standing by the entrance at evening rush hour, you can fix your ex-to-be with a wistful gaze. "I'm sorry," you can mutter over the din, "I'm just . . ." -- here a treacly smile will do -- "not good enough for you." Then, raising your hand for that last insouciant flourish, you can watch him/her descend gently into the abyss on the longest escalator ride in the Western World (that's 194 feet, 97 as the shoe drops). Note: If Rosslyn's inconvenient, try Dupont Circle, whose escalator's only slightly shorter.

More Easy Letdowns: You might agree to meet your mate in Langley late one night, outside Central Intelligence Agency headquarters. "I've been less than truthful with you," you start off, "I don't really work for the Seven Eleven." From your trenchcoat, produce a pair of dark glasses and slip them on. "I'm off on a secret mission and probably won't be back."

Or, after supper in Baltimore, you can suggest a waterfront stroll in nearby Dandalk, Maryland, to check out the barges and cranes. By the time you get to the passenger terminal -- if it's around 11 o'clock May 19 -- a Cruise International liner will be sailing for Bermuda. "Wait here, dear," you can say, then charge up the gangplank as the crew pulls it in, tossing the car keys (if you're a decent sort) on the dock.

The ideal breakup may not be all sweetness and light, but neither is it the mess most of us seem determined to make of it. The breakup can, if only we'd let it, emerge as a work of art.

For style and grace, it's hard to top Humphrey Bogart and Ingrid Bergman on the tarmac in Casablanca, but you can try at the Eastern Airlines Shuttle amid the throng at National Airport. As both of you lean on an automatic ticket dispenser, one of your might start:

"Last night we said a great many things. You said I was to do the thinking for both of us. Well, I've done a lot of it since then and it all adds up to one thing. You're getting on that plane where you belong."

"But, no, I, I --"

"Now you've got to listen to me. Do have any idea what you'd have to look forward to if you stayed here? Nine chances out of ten we'd both wind up in the Bureau of Traffic Adjudication, trapped forever."

"You're saying this only to make me go."

"i'm saying it because it's true. . ."

The preceding, an example of a type of breakup known as The Short Shrift, always works -- maybe not today, maybe not tomorrow, but soon, and for the rest of your life.

The no-frills variation has you and him/her at the Greyhound Bus Terminal downtown.Should the point fail to sink in, just cross 12th Street to the Trailways Terminal and try again.

Literatti can say it with a book (The End of the Affair, How to be Your Own Best Friend or The New Celibacy might fill the bill).

Bureaucrats can say it with a memo. Politicians can say it with a press release. Adn diplomats can declare each other persona non grata by making a date for the next soiree at the Iranian Embassy.

If you're journalistically inclined, announce that you're on the verge of breaking a major scandal ("This could be bigger than Watergate"), and that you'll need only a year of constant toil to sort it out.

To throw over a Department of Agriculture entomologist, insist on a rendevouz at the praying mantis case in the National Insect Zoo -- he/she will grasp you terrible intent.

The career military method (works best in the Army) involves requesting an extension of your Pentagon tour. Your orders for the St. Louis supply depot should arrive soon after.

Highbrows, meanwhile, can try it at the National Gallery, at any number of paintings treating the explusion from the Garden. If vulgarity's called for, drag a highbrow to an all-night bout of professional wrestling at Capital Centre, featuring Haystack Calhoun, Moose Monroe and a Texas Suicide match, wherein the grunting oponents are suspended above the ring in a tiger cage. Buy him/her a flat beer and burger and say you won't leave till it's over.

You can end an inter-office tryst with a bogus wedding announcement (not to your ex-to-be) in the company newsletter -- tacky maybe, but cheap.

By way of parting shots, present a devotee of the National Wildlife Federation a pair of Canadian sealskin slippers, take up smoking to banish a staffer of the National Clean Air Coalition, become a vegetarian to put off an American Meat Institute lobbyist and suggest a weekend in Pittsburg to a Sierra Clubber. To an inveterate theatergoer, hint darkly that you'd like to see "I'm Getting My Act Together and Taking It on the Road" (at Ford's Theater through February 22).

Mystery fans can concoct a slew of cleus: shirts redolent of odd perfume, hickeys wrought with the vacuum cleaner and a bushel of self-sent flowers should conspicuously do the trick.

And, don't forget, there are at least seven tattoo parlors about town that will gladly affix an unfamiliar name to a familiar part of your body.

The bald-facedly commercial, meanwhile, can dash to the local stationer's, where cards such as "I can see the future / And you're not in it," courtesy of TNT Designs of New York, and a red heart stamped "It's Over," from PPB Designs of Dallas, are up to the job. "They're selling quite well," reports Pat Bailey of PPB. "Must be some cold-blooded folks out there."

If you're fiscally responsible, invite your mate to Tiberio on K Street, but end up next door at McDonald's. "David Stockman made me do it," you can explain. If you're eating Chinese, bride the waiter to slip inspecial fortune cookies -- "Absence makes the heart grow fonder," for instance -- after the Peking Duck. Or just start bringing your mother with you on all your evenings out.

Then there's always philosphy: Altruism ("This is for your own good"), Utilitarianism ("This is really best for all concerned"), Skepticism ("I doubt we can go on like this") or Stoicism ("We're having too much fun") might do for openers. In a pinch, try Sophistry ("We could keep going out -- I'd like that -- but it would be wrong").

For a Sunday Surprise, try an afternoon stroll through Adams Morgan, to Kalorama Park. "Whaddaya know," your ex-to-be will exclaim, "a hot air balloon!" For a C-note, there it'll be, bright and beautiful, bobbing on its tether in the breeze. As you jump into the gondola, flash a blinding smile and chirp, "You've been such a good sport. Cheerio." Then float away. Kevin Poeppelman of Adventures Aloft (660-6066) will make the arrangements.

As a last resort, acquire a motorcycle and sidecar at a police department auction (the next one's at 9 o'clock the morning of March 3, at the Blue Plains impoundment lot) and invite your mate on a day of Washington sightseeing. As you start down Meridian Hill, turn to him/her and say, "There's something I've been meaning to tell you, hon, but I don't know quite how to put it." Then pull the linchpin and veer sharply into a sidestreet.

The message couldn't be clearer.