How many times has this happened to you?

You've worked hard all your life at the foreign ministry, you're rewarded with a top position at the embassy in Washington, you polish your English and head for America with a patriotic smile on your face.

You take your first call. A Well-Placed Friend is trying to help you:

"Thanks for picking up, Mr. Ambassador. Just got off the horn with State. There's some flack about that ballot-stuffing baloney. Could get nasty on the floor -- maybe a filibuster, who knows. Look, what say you show at our shindig Wednesday, slap a few backs, squeeze a few hands, flirt with the press till this cools. Hang tight, sir. We're all pulling on this."

The future of your country may be in your hands, but you may make the wrong decision because you can't understand a word. That is, you understand the words until they're strung together.

Your troubles may soon be over. Starting tonight, the Smithsonian Resident Associate Program offers a five-week course in "American English in Washington, D.C." for diplomats and other foreign residents who can't get the hang of American idiomatic expressions. It should be a knockout.

The course, which will cover the psycho-linguistically distinct dialects of Media English, Commercial English, Government English and Cocktail English, was designed by Kathleen Diamond, owner of Language Learning Enterprises. Diamond, whose company normally teaches everything from Spanish to Wu (a Chinese dialect), wanted to do something fun when the Smithsonian called her in to develop this never-before-offered course.

"All you have to do is watch TV, listen to the radio or look at advertisements in newspapers and magazines to realize there are things in English not comprehensible unless you understand the American idiom," says Diamond.

The instructor will be Pamela Monder, a University of Maryland master's degree candidate in "Teaching English as a Second Language" who has done just that in New York City and Belo Horizonte, Brazil.

Diamond saw the demand for idiomatic education when a neighbor said to a French friend who'd gone to a baseball game, "That must have been a treat for you." "The foreigner's going to pull a complete blank," says Diamond. "What does 'that must have been a treat' mean to a foreigner?"

The course could be called "Everything You Always Wanted to Know About Everything You Were Supposed to Know but Were Afraid to Ask." Among the problematic, idiomatic mind-mixers the students will finally learn:

In Media English: glitter, deejay, banner headline, yellow journalism, censorship, X-rated.

In Commercial English: three-martini lunch, Muzak, "let me give you my card," "put it on my tab," "put your John Hancock here."

In Government English: mudslinging, hung jury, ambulance chaser, jumping bail.

In Cocktail English: flirting, mingling, breaking the ice, yuppie, finger foods.

Also on the curriculum are common words derived from American brand names, such as Xerox, Kleenex, BVDs and Pampers.

Maybe the course could also be called "American Culture and You: Getting Out Alive."

There will be role-playing in telephone conversation and cocktail party behavior to see "how the words reflect cultural habits," says Diamond. "We have the word 'finger food' because we eat with our fingers at cocktail parties. In many countries you'd never do that."

Source materials will include Gary Goshgarian's "Exploring Language," Jonathan David's Dictionary of Popular Slang and journals that aren't quite scholarly but fit the bill: Soap Opera Digest, TV Week, Rolling Stone and National Lampoon. Should be gold mines.

The Government English session will feature audio-visual aids -- namely, Harris Miller, Fairfax County Democratic chief, and Christophe Tulou, legislative director for Rep. Tom Carper (D-Del.). Asked what he plans to say, Tulou responded: "Oh, brother . . . I don't have a good grip on that." He said he wants to give the students "a fighting chance" in Washington. It's a jungle out there, and if you don't understand that, get out of Washington.

The course meets Wednesdays at 6 p.m. until Aug. 20. The fee is $65 for members of the Smithsonian Resident Associate Program or $95 for nonmembers. Call 357-3030 to register.

And if the person on the other end asks, "How's it going?" just say, "Very well, thank you. And how is yours going?"