First, it was dress for success. Then, it was talk for success. Now, it's etiquette lessons.

"It's been chaos in the manners department," says Letitia Baldrige.

"It's no longer acceptable to be a clod," says Marjabelle Young Stewart.

"Both socially and in business, if we don't like the way people behave, we have less and less inclination to put up with them," adds Forrest Winquest.

All three etiquette mavens blame the disintegration of manners -- at least in part -- on the rebellious 1960s when traditional values were rejected.

Stewart traces their newfound importance to Ronald Reagan.

"He's the most mannerly president we've ever had," she asserts.

Indeed, since his 1981 inauguration, bookstores are stocking more etiquette texts. The consulting business is booming. More and more classes in etiquette are being scheduled by colleges, adult-education programs, cooking schools and even those marketing hotel entertainment and vacation packages.

Of course, adds Stewart, we can't forget the Yuppies. "They are going places, doing things" and they've discovered that good manners help them make the move up more gracefully.

What exactly does it mean to be mannerly?

"Treating others as respectfully and considerately as you would like to be treated by them. Not finding fault," says Winquest of Silver Spring. "Making others feel comfortable but not at the expense of making yourself uncomfortable." She teaches etiquette both at the Learning Annex adult-education program in the District and at L'Academie de Cuisine cooking school in Bethesda.

"Think of the rules of etiquette as the road signs of life. Manners pertain to your behavior once you have those rules," says the Kewanee, Ill.-based Stewart, who spreads the gospel of politeness monthly on the TV talk-show "Hour Magazine" and is author of The New Etiquette: Real Manners for Real People in Real Situations -- An A-to-Z Guide, (St. Martin's Press, 1987, $22.95).

"Manners keep us human in the age of machines," adds Baldrige of New York City. "They make everyone feel good."

Stewart gives a couple more examples of mannerly people.

"Nancy Reagan: With that lovely serene smile, she can give you an answer that works even if it has nothing to do with the original question.

"Bill Cosby: He treats his TV family with respect, building their egos rather than tearing them down."

When pressed, she cites ABC-TV newsman Sam Donaldson as an example of an unmannerly individual "because of his demanding tone of voice when he asks the president a question. What a rude kind of role model he is for children, but President Reagan never comes unglued."

While "etiquette" may not yet be a buzzword, the subject is generating an ever-increasing amount of interest in the business world.

Says the author of Letitia Baldrige's Complete Guide To Executive Manners (Rawson Associates, 1985): "Good manners are cost-effective. Not only do they increase the quality of life in the work place, contribute to optimum employe morale and embellish the company image, but they play a major role in generating profit."

Since etiquette is such an important rung up the ladder of success, what should we be teaching our children to lay the groundwork?

"Before you teach children the correct way to hold a tennis racquet or golf club, teach them how to hold the tools of the table," says Stewart. "They may have been born with a silver spoon in their mouth, but they still need to learn how to use it. Good manners are their inalienable right.

"Next, instill in your children respect and consideration for the family. Here are examples: It is just good manners to take a proper phone message. It is just plain considerate to fold the paper back into its original condition after reading it."

Baldrige adds to the list: "Be aware of your behavior at all times. When someone is at a loss for words or makes a gaffe, help him out. Learn how to express yourself in writing. Be able to put your emotions on the record -- thank-yous, apologies, congratulations, sorry about the loss."

"Knowing the correct thing to do builds confidence," concludes Winquest. "Of course, you don't want to take it too seriously. Be able to laugh at your mistakes. Everyone makes them."