Sending back a spoiled wine can be intimidating, but you can pull it off smoothly if you follow these guidelines.

Some friends of mine ordered a bottle of wine in a small neighborhood restaurant recently and found it to be spoiled. When they complained to their waitress, she replied, "What do you mean, it's no good? You saw me open it right in front of you." The owner, who admitted that he never drank wine, sided with the waitress.

Although I've been writing about wine for many years, I still experience a moment of anxiety from time to time when ordering a bottle in a restaurant. What if there's something wrong with it? Will it lead to an awkward confrontation? I know I'm not alone in wanting to avoid a scene, especially when dining with friends. Other wine professionals also have qualms. Larry Stone, the wine director at San Francisco's Rubicon, says, "Sometimes I'm afraid to speak up myself. There's always some suspicion surrounding anyone who complains about a corked bottle."

Of course, some customers are more adept than others at handling that sort of anxiety. Rodney Strong, founder of the eponymous Sonoma, California, winery, once ordered a bottle of La Tâche 1962 in a San Francisco restaurant and discovered it was spoiled. When the sommelier insisted that the bottle was good, Strong patiently explained, in some detail, what was wrong with the wine. The sommelier, fascinated by the analysis, got a second bottle, opened it and sat down with Strong to continue the tutorial.

Unfortunately, most bad wine served in restaurants doesn't get sent back. Professional tasters, who sample hundreds of bottles, suggest that a spoilage rate of five percent is not unusual. Rubicon's Stone pretastes every wine served in his restaurant. "I'm more severe than our clients, and I reject about eight percent of the wines we open," he says.

Armed with this knowledge, how can one best approach the ritual of restaurant wine service? To begin with, once I've chosen a wine, I ask to have it brought to the table as quickly as possible; if there is a problem, I need to resolve it before the food arrives. After I've confirmed the name and vintage, I make sure the waiter pours enough wine into my glass--at least an ounce--so that I can evaluate it properly. The first indication that there may be something wrong with a wine, whether red or white, is its appearance. A sound wine is brilliant and translucent, a poor one dull and opaque. If a young white is dark, or a young red has an orange cast, there's bound to be trouble ahead.

Most wines reveal their flaws by their aromas. If a wine smells clean and fresh, it's likely to be fine, though you may want to take a sip to be sure. (Note: If a white is served very cold, its aroma and taste are suppressed; the wine needs a few minutes in the glass to reveal its qualities--good or bad.)

The most common cause of spoilage is a contaminated cork, which affects the smell and taste of the wine. (The cork itself may not reveal the problem, however, so don't bother smelling it.) A corked, or corky, wine--the terms are interchangeable--has an unpleasant aroma like wet cardboard, a damp and moldy basement or a dirty gym locker. Sometimes an old wine will smell musty when first poured, the result of extended bottle age, but this will disappear after a few minutes in the glass. The bad smell and taste of a corked wine, however, never go away; in fact, they are likely to get worse.

Another problem, less frequently encountered, is oxidation, possibly caused by a faulty cork that let air into the bottle. Excessive age may oxidize wines as well. An oxidized white looks unnaturally dark; its aroma is stale rather than fresh and fruity.

Then there are other, even more unlikely problems, such as the one encountered by British wine writer Jancis Robinson at a dinner in Scotland. She had ordered a fine old red Burgundy but sent it back because, she says, "the bottle had been put on a hot plate to take off the cellar chill, and by the time it was poured out, steam rose from the glasses."

If you are served a spoiled wine, bring it to the attention of the waiter or sommelier immediately, perhaps saying something like, "I've enjoyed this wine before, and this bottle doesn't taste right. Would you try it?" While some restaurateurs may hesitate to replace a bottle, most are eager to deal with a diner's discontent. As more than one restaurateur has observed, "We don't want to lose a customer over a bottle of wine."

Jean-Claude Vrinat, the owner of Taillevent, a luxurious Paris restaurant known for its outstanding wine list, says, "The client must never lose face." He recalls a diner who ordered a bottle of Vosne-Romanée and, when it was poured, said, "This doesn't taste like Pommard." Rather than embarrass him by pointing out his mistake, Vrinat replied, "It must be the glass," and brought a clean one, by which time the man had realized his error.

Some wine problems have more to do with experience or expectation than with flaws. When tasting a wine in a restaurant, remember you're just making sure there's nothing wrong with the bottle, not evaluating its overall quality or potential. (This is why, if you order a second bottle of the same wine, the waiter should bring you a clean glass to taste it, too.)

There are people who may reject an unusual wine because they aren't familiar with its taste or character. The heavy style of a white Rhône, for example, or the assertiveness of a Sancerre may be surprising, just as the acidity of a white Burgundy may put off someone used to the richer style of a California Chardonnay. Similarly, the restrained, slightly faded qualities of an older red Bordeaux may disappoint someone who usually enjoys young Napa Cabernets.

A good sommelier will discreetly sound out clients who order old or esoteric wines to make sure they are familiar with the taste. The sommelier wants to avoid having the bottle rejected, of course, but also wants to prevent an even more unsatisfactory scenario, in which the customers say nothing and suffer through the meal with a wine they don't like.

Happily, not only is wine service in restaurants today more knowledgeable than it was in the past, but so are restaurant patrons. It wasn't so long ago, after all, that restaurateurs had to be on their guard against people who liked to send back expensive bottles just to show off.

André Surmain, who founded New York's famed Lutèce restaurant with chef André Soltner in the early 1960s (and who now owns Le Relais à Mougins, in the south of France), recalls how he dealt with such customers. He had assembled a cellar at Lutèce that included many old and rare bottles. When someone ordered a very fine wine, Surmain brought it to the table himself, along with a decanter and an extra glass. Said Surmain, "I personally decanted the wine over a candle, poured a little into my glass to taste, and if the wine was all right, turned to the host and said, ‘How I envy you this experience.' Let me tell you," Surmain continued, "it took someone with a lot of chutzpah to send back a wine after that."

Alexis Bespaloff has written five books on wine, including The New Frank Schoonmaker Encyclopedia of Wine.