“Why can’t you behave?” plaintively asks the old Cole Porter song. “Why can’t you be good? And do just as you should?” Original sin always seems to me a good working hypothesis, but it doesn’t offer practical advice on how we can emend our behavior. Much less the behavior of those inconsiderate oafs and boors around us.

One dispenser of practical social advice is the absolutely fabulous Mary Killen, whose column, “Your Problems Solved,” appears at the back of the London Spectator. She ingeniously devises solutions so as to arrange matters for her correspondents’ convenience. I’ve got a mental note about a letter that asked how one could avoid inviting one’s boring old great-aunt to one’s wedding without wounding her feelings and forfeiting the nice-silver-something she would otherwise send as a present. Sometimes the advice-seekers are blunter. Here’s “Name withheld, London W8”: “I am absolutely infuriated to hear that some very great friends of mine are giving a dinner party next week to which they are not inviting me. This has happened once too often. How can I get my revenge?”

I gurgle and chortle as I read Dear Mary’s responses, but it is clear that she is not appealing to the better angels of our natures. And that’s why I always ask myself, as an American, “What would Lincoln do?” Since he died before getting around to writing his thoughts on etiquette, I generally turn to Miss Manners – the nom de plume of Judith Martin – whose classic “Guide to Excruciatingly Correct Behavior” (W.W. Norton, 864 pages, $35) has just been updated and reissued. It’s a wonderful compendium of advice for dealing with what she calls Beginning, Intermediate, and Advanced Civilization.

Those great practical men of the Enlightenment George Washington and Thomas Jefferson thought less about the details of proper fork placement than on the fundamental principles underpinning manners appropriate for the citizens of a new republic. Even in these revolutionary matters we should have, in the words of the Declaration of Independence, “a decent respect to the opinions of mankind.”

Miss Manners thinks theirs was a “noble endeavor,” even if she disagrees with some of their conclusions. Washington was concerned with maintaining the dignity of the office in the eyes of the world. Fortunately, on the matter of addressing the president, other voices prevailed; we use “Mr. President,” rather than Washington’s suggestion, “Your High and Mightiness.”

Contrariwise, Jefferson, in his “Memorandum on Rules of Etiquette,” showed himself to be a rank leveller: “When brought together in society, all are perfectly equal, whether foreign or domestic, titled or untitled, in or out of office.” So Jefferson favored round tables and no seating plans, and he entertained foreign visitors so informally – in his slippers – that they weren’t sure if they had been officially received at all.

But how do we show courtesy if we’re all equal? Nowadays, one does not have to search far to find supporting examples for the view that a nation of entitled individuals makes for rude compatriots. More advice about the use of forks is not going to help. Miss Manners follows in the footsteps of Washington and Jefferson in trying to find, as she puts it, “a philosophically acceptable and aesthetically pleasing standard of American etiquette.”

The case of curtsying to royalty is easily dealt with: “Bending the knee is the traditional gesture of an inferior to a superior. We bend our knees to God, or whatever it is that we worship – debutantes traditionally curtsy to society, for example.” Thus Americans, no matter how many ballet lessons their parents have paid for, do not curtsy to royalty. The simple and dignified handshake is always suitable.

Here’s a thornier class of examples: If we’re all social equals, how do we treat the people who are temporarily “below” us? Is it polite to get chummy with the waiter? What about the people “above” us? Your boss might invite you to her son’s bar mitzvah, but she can still fire you. Americans have historically defined themselves in terms of work, and today there’s very little real private life left. The blurry lines between work manners and social manners are lying about everywhere to trip us up.

The workplace is one area where Miss Manners’s common sense is indispensable: “It is vulgar to discuss money socially and impossible to do business without doing so.” Seems simple, but, as she points out, women entering the work force who confuse social and business talk are “reluctant to ask for raises.” It pays to listen to Miss Manners.

On sexual harassment she is equally bracing: “Miss Manners must warn you that etiquette does not have a good record in discouraging this sort of thing. That is why the law had to step in, once society finally acknowledged the seriousness of the problem.” Her recommendation: Using unthreatening but vaguely legalistic terms, keep making your feelings known “up the chain of command until you get to someone who – regardless of his own feelings or behavior – has the sense to get frightened.”

Her response here displays another admirable aspect of Miss Manners’s advice: She does not confuse manners with morals. Unlike the utopian forces of political correctness that would like us all to think the same thing, Miss Manners limits herself to reforming our behavior. That is surely a big enough task for anyone.

To that end, she advocates social dissimulation – otherwise called “hypocrisy” by the unsympathetic. She points out that there are “deeply felt emotions that ought never to be expressed by anyone,” and she feels that “what the world needs is more false cheer.” In these days when rudeness and counter-rudeness, and the determination to give and take offense, are escalating, she also has a refreshingly novel attitude toward blame: “If everyone takes a little blame, there will be less of it going around.”

At its most basic, etiquette implies a basic social contract: “the reluctance of most people to persist in annoying and angering others.” New technology has of course increased the ways in which people can be annoying.

Dear Miss Manners: We are eloping and sending out announcements after the fact. … Does anybody have a good way to request gifts of money? We are thinking about putting up a personal website about the wedding (with the URL on our “we’re hitched” announcement) and maybe having a line to Paypal. Is this really offensive?

Miss Manners’s answer is a model of how we might behave. First, she avoids getting in a huff while still making her position clear: “You may be surprised to hear that Miss Manners is not in the extortion business, so she cannot advise you how to do this.” Then, she applies new technology to this old problem of human greed: “The inoffensive thing is to ignore the issue of possible gain. You may even do better in the end by leaving this to the voluntary generosity of your family and friends and discreetly using the Internet to auction off the take.”

In the latest “Guide,” etiquette questions based on the changes in technology are beginning to make Miss Manners a bit tetchy: “The old rules about not interrupting events or ignoring people who are present or pestering people who are absent should prevent these items from being used rudely.” The more interesting questions arise from changes in social behavior. Sometimes the application of old rules to new situations is easy. Question: How do you greet a gay couple? Answer: “How do you do? How do you do?”

Miss Manners also issues a salutary reminder about the limits of etiquette. If you’re having an illegitimate baby, by all means send out a birth announcement. On the one hand, even though a birth announcement is not an invitation for others to give their opinion, don’t expect approval from everybody. On the other hand, “What you should expect is tolerance, and you are quite right to be insulted when you are the target of mean remarks. The reply to such is a frosty “How kind of you to point that out.”

Whether you’re in the market for manners or sociology, the “Guide to Excruciatingly Correct Behavior,” at almost 900 pages, offers hours of instructive and delightful reading. And, if you’ve got a taste for it, Miss Manners can be thought-provoking to boot. Above all, her greatest skill lies in rethinking and retailoring the symbolism of manners without ever for a moment doubting the necessity for having manners in the first place. This is, after all, the American, rather than the French, revolution in manners.

Ms. Mullen is a contributing editor of the Hudson Review.