One reason tipping creates such anxiety is that it attaches a price tag to human interaction. Perhaps that's why, as Guy Trebay explains, it may be best to tip with your heart—and forget about formulas.

I tip wrong—too much or too little. I tip emotionally, exactly as the experts say never to do. I tip for results and don't get them, or according to who's watching or to what I have on me. Sometimes—hotel doormen—I tip not at all because, like most people, I rarely arrive in foreign cities with the correct and respectable amount of yen or euros rattling around in my pocket.

And what is the right amount?It's a riddle for the ages. Most tipping guides, it strikes me, are about as useful in the creakiness of the formulas they offer as in the somewhat dubious factoids on tipping history they tend to provide.

Is tipping really an invention of the Middle Ages?Or did the custom get its start when 16th-century tavern patrons tossed coins on the floor to inspire tankard-hauling wenches to speed up the service?Or can the word have originated, as the authors of The Itty Bitty Guide to Tipping propose, in a London pub where there was a bowl labeled TO INSURE PROMPTITUDE? Logic, I'm afraid, suggests otherwise, since leaving something in a tip jar is no guarantee of much.

To follow the advice of the countless etiquette books and laminated pocket guides and primers that address the subject is to conclude that tipping correctly is a matter of transforming oneself into an ambulating ATM, spitting out bills to anyone who pulls a lever on a coffee machine. Typically the advice can be reduced to one general and almost universal formula: tack 15 percent onto any bill, add roughly $2 to any exchange not regulated by tariff, and remember that tipping is considered gauche in Japan (not really true anymore).

While these books sometimes make for amusing reading, they rarely offer guidance on how to deal with the low-level anxiety that is their obvious reason for being in the first place. They fail to address the resentment that has largely supplanted gratitude now that nearly every human transaction is tacitly subject to surcharge. And they certainly don't take into account the power of public ridicule. See, please: (Although you might want to skip this sewer of on-line vitriol if you tip like Howard Hughes or if your name is Jennifer Lopez.)

Don't get me wrong. I believe in reward for service. I respect honest labor. I deplore the conditions under which many people toil at jobs where they are expected to compensate for income shortfall by becoming "lovable" gum-cracking hash slingers like the kooky cartoon waitress Cher used to play on TV. Although I am assured that few people do it anymore, I take pleasure in supplementing the wages of most hotel housekeepers by leaving my daily five bucks on the pillow, inside a hotel envelope with grazie or merci or danke scrawled on the front. Even that act, however, has its roots in superstition, the sense that by recognizing the existence of the mostly invisible person who cleans my room, I may stave off pilferage or, worse, becoming the victim of an art project, as happened to the hapless hotel guests whose habits were ruthlessly documented by the French "artist" Sophie Calle while posing as a maid.

And, let's face it, tipping is generally an elaborate form of paying baksheesh. I accept that. At a hotel where I used to stay in Paris, my first stop before heading to my room was always the concierge station. There I performed what I think of as a good impersonation of masculine assurance, grasping this man's hand in a hearty handshake while slipping him an envelope. The exchange was a form of Kabuki, a theatrical moment during which we each conspired to imagine that this gesture was a subtle token of mutual understanding and nothing as Enron-grubby as a bribe.

But a bribe it was. The man so proudly kitted out in his canary vest and midnight blue tailcoat understood this. Being a travel realist, so did I. Among the doors to be opened by the gleaming keys he wore on his lapel were those to Le Voltaire, the superb dining place where getting a reservation is impossible unless you were christened Catherine Deneuve or have a fixer from the global concierge mafia on your side.

Yet success is not guaranteed, even at that. One season, this concierge suddenly failed me, and not just at Le Voltaire but also at Benoît and even at the homey little Right Bank place where I have often dined. What went wrong, I wondered?Had I forgotten to factor a COLA increase into his envelope?Where had the smile gone, the warmly phony bonhomie?In their place was that expression of resignation the French delight in assuming when resorting to the most enduring of Gallic defaults: "So sorry,'' he told me. "It is impossible.''

I no longer stay at that hotel. A deal, however iffy or rigged, is a deal. Likewise, a cup of coffee is just that. "Next time you get your tall triple-shot almond latte with whipped cream at 8 A.M., remember that the person who made it was probably at work three hours before you hit the snooze button,'' a blog-ger recently ranted on a tipping Web site. How much of that barista's tip-cup cream, one wondered, was skimmed off for the Kenyan coffee pickers who would probably consider a dawn wake-up call the greatest of life's luxuries?

This is not just a rhetorical question. The least venal part of the tipping transaction is the one that concedes the existence of others, the chain of interdependence linking all of us along the chain of supply.

Whether in wealthy countries like France (where waiters are paid properly), or in what used to be called the Third World (where calculating tips in local currency and according to prevailing economies becomes both a nagging dilemma and a kind of joke), it seems important to be generous, dispensing largesse while keeping in mind that life is not a Jerry Lewis telethon. Tip badly, irrationally, all wrong, is my policy now. Then let go of the issue. Whatever I don't palm to a doorman, I tithe in a monthly envelope sent to charity.

Guy Trebay is a reporter for The New York Times.