It was one of those intime elegant Georgetown dinners--a few top Washington journalists, an ambassador or two, a couple of leading political attorneys--maybe 14, 16 people in all.

And it was elegant, not only in its menu, but in the accompanying alcoholic beverages. Cocktails first, of course, then a light white with the fish, a nice little imported rose' with the meat, champagne brut with dessert.

After dinner the group moved to the den to watch the president's speech that was being televised that night. A couple of scotches, perhaps, or cognac or B&B or another liqueur . . .

We're not talking about alcoholics here, mind you. Not even people who drink more than a glass or two of wine a day, if that. The social drinker, the weekend drinker, the occasional drinker.

That night's occasional drinkers were of the fine and upstanding persuasion. Solid citizens, opinion molders, social consciousness honed to a fine point, very much aware of and sympathetic to the grassroots movement to "do something" about drunk drivers.

But suddenly, sipping that nice little rose', someone wondered aloud if they just might be talking about themselves . . .

I still remember the boy that was killed in an auto accident in my high school class. I didn't even know him very well. I heard that there'd been a lot of drinking involved. That was some 35 years ago. I don't remember what he looked like too well anymore. But I remember his name.

If anything, the situation has worsened. The Federal Traffic Safety Administration estimates that 60 percent of young people between the ages of 16 and 24 who are killed on the highways were involved in alcohol-related accidents.

How can anyone tell if he or she has had too much to drink?

By and large, the answer is that while you are drinking, you can't.

People, well meaning as they may be, who are looking for easy answers aren't going to find them.

"Alcohol," reminds Dr. Ralph Ryback of the National Institute on Alcohol Abuse and Alcoholism, "is a drug. There is no way around it. It has very potent effects, especially on those who have little experience with it--as is the case with anything that causes stress. And alcohol causes stress on the brain."

As a central nervous system depressant, alcohol affects cognition and volition--including motor skills and speech, but also the ability to process abstract thoughts, make judgment calls, react reflexively--"all those things," says Ryback, "which don't let people function as they should.

"Even the glare reflex is impaired. People wonder why they have such trouble being able to see . . . "

Here is the dilemma, says Ryback, a veteran medical specialist in alcohol abuse and treatment:

"The person who just drinks occasionally is invited out to this wonderful celebration. It's one of those things like a buffet--how can you turn down something that's so nice? A lot of self-discipline is lost right there. And once the person takes a couple of drinks, even more is lost.

"Non-drinkers at a cocktail party notice that after about the third drink, they're no longer talking to a person, the person is effectively gone.

"We know from cocktail chatter that at the start the conversation may be at say, the 11th-grade level, but with successive drinks it will drop to the 4th grade as people are unable to bring to mind words and concepts, as in 'What was that you were saying about Reaganomics? . . . I don't quite understand . . . I only know the *! ** is losing all our money . . . ' "

By the same token, the person who has had two or three successive drinks is no longer capable of judging whether he or she has had too much or how long ago it was since the last drink, much less whether he or she is capable of driving home.

Charts, some of them conveniently wallet-sized, purport to help folks determine how much alcohol imbibed within certain time limits will affect people of varying weights.

They are, believe many experts, including Ryback, less than useful.

It is true that one drink (of 1/2 ounce alcohol or 1 ounce of a 100-proof whiskey, for example) every two hours will probably give a healthy 160-pound man's liver ample time to process out the ethanol, therefore preventing any buildup of alcohol in the blood.

But this is only true if:

* His weight is mostly in muscle, not in fat.

* He is eating food along with the drinks.

* He is under no unusual stress, is neither angry nor especially euphoric, nor frightened, nor moved by any other strong emotion.

* He is taking no other drugs. Especially not any sedatives, tranquilizers or antidepressants and not even over-the-counter drugs as found in hayfever or allergy medicines, cold remedies, cough syrups, even aspirin. Some of these drugs interact synergistically with alcohol--the effect of the two together increases the effect of each. And aspirin's tendency to irritate the stomach may be exacerbated by alcohol.

Also, says Ryback, this presupposes that all drinks are measured and "you'll go to a party with a stopwatch and a measuring cup: 'Oh, sorry, no red wine until 9 o'clock . . . my liver is sluggish tonight . . .' "

Because the fact of the drink itself prevents the drinker from being a judge of his own capabilites, Ryback and others are increasingly persuaded that more responsibility should be placed on the shoulders of the server, whether it be bartender or host or hostess.

In some states, including New York and California, laws are increasingly making "servers" liable for damages and injuries inflicted by the drinker on him or herself and others.

When he tackles the American way of entertaining, Ryback realizes he is wrestling with a built-in social phenomenon that finds hostesses (and hosts) helplessly convinced that if guests do not partake of the food and drink proffered, it is a sign of rejection of the hosting party's generosity, therefore a rejection of host and hostess themselves. He recognizes that it is "anti-American, anti-intellectual, anti-cultural . . . "

Nevertheless, he says, "The issue with alcohol is that the very control center we value so much, that seeks to enjoy fine wines and liquors is lost in trying to enjoy it."

He would like to see people check their car keys at the door of a saloon or party just the way the Old West heroes checked their guns. And for exactly the same reason.

He urges that those who entertain not assume that "the consumption of alcohol is synonymous with the success of the affair."

At least, he suggests they recognize that "drink may be a lubricant to one's sociability, but it shouldn't, by marinating the guests, take them out of social interaction and make them a danger to themselves and others."

Other suggestions for teen-agers and others:

* When you go out drinking, arrange in advance to spend the night at someone's home just in case.

* Eat when you drink. If you're entertaining, be sure there's plenty of food.

Sip for enjoyment, don't gulp.

* Don't drink to relax. What you probably need is a nap. Or a run around the block.

* If you go out with a group on a regular basis, rotate the driver-for-the-evening and restrict him or her to one beer. For special nights, like proms, draw straws.

Remember that when everyone else around you is tipsy, you can feel tipsy yourself WITHOUT ACTUALLY LOSING CONTROL. illustration: Drinking