By John Mariani

updated 3:09 p.m. ET Aug. 8, 2008

Comedian Fred Allen once defined a celebrity as “a person who works hard all his life to become well-known, then wears dark glasses to avoid being recognized." Which is why, when you enter a restaurant, the only people likely to be wearing sunglasses are either recovering from eye laser surgery or go by only one name, like Madonna, Angelina or Uma.

Even if sunglasses don’t completely disguise a celebrity from view, they have a certain “do-not-disturb” effect in a restaurant, lest a fan wants to bound over for an autograph while the celeb is seasoning her Caesar salad.

But let's be honest—spotting a celebrity, whether from the world of entertainment, sports, media or politics, gives a real buzz to an evening dining out. For some people, such sightings are more important than the food. Simply being in a place where Alex Rodriguez, Demi Moore, Brian Williams or Ted Kennedy dine makes the celeb-watcher feel part of the aura thrown off by the star.

Once upon a time, in Hollywood’s Golden Years, celeb sightings were relentlessly covered by the tabloids as part of the studios’ own publicity machines. Thus, a new starlet would be hooked up with an established star and sent to the Copacabana or El Morocco expressly for the purpose of having their pictures taken by the photogs.

This endures to a certain extent today at celeb-flocked restaurants like Spago and Mr. Chow in Beverly Hills, which count among its guests everyone from George Clooney to Elizabeth Hurley, whereas it is discouraged (though not unknown) in New York. (When Madonna and Guy Ritchie recently went to ‘Cesca on the Upper West Side, they were greeted by a phalanx of paparazzi outside the Italian eatery’s entrance.)

Many restaurants confer with celebs’ “people” as to the best tactics to avoid the paparazzi at the front door. The manager of the Sunset Marquis in West Hollywood, where villas rent for up to $7,000 a night (and whose boast is: “Movie stars get big trailers. The really big stars get us.”) told me that if a big star like Madonna is dining at their intimate restaurant, The Room, she may be ushered through the service hallways to a back door while a double in sunglasses whooshes into a waiting limo at the front door.

More from ForbesTraveler.com Click below for more slide shows Celebrity spas Celebrity 100 getaways Top celebrity vineyards World's top restaurant cities Celebrity-owned restaurants

But for the average diner who wouldn’t mind sitting across from a celebrity, there are, in fact, rules of behavior. First and foremost, it's tacky to ask for an autograph. If seated next to a celeb, a simple nod of recognition should be all you allow yourself of intimacy. Celebs may well want attention, but on his or her terms.

In a place like New York’s Balthazar in Soho, the chances of spotting someone from the entertainment or fashion business is very high; many of those industry’s celebs either live or have offices in the area, like Martha Stewart, and on any given day you might find Bill Gates lunching with Bono.

Nobu With owners like Robert De Niro, Harvey Keitel, Bill Murray, Mikhail Baryshnikov, Sean Penn, Ed Harris and Christopher Walken, you can bet on more than occasional celeb sightings. They come for the inventive sushi and modern Japanese cuisine.

Bill Cosby frequents New York’s Le Cirque in Midtown, and literally gets up from his table and goes around the room to kibbitz with the restaurant’s guests. In fact, Le Cirque is one of the city’s best-known celeb hang-outs, and counts among its regulars Woody Allen, Barbara Walters, Henry Kissinger and Paloma Picasso. Once, when a non-celeb newcomer complained that the tables were too close, Le Cirque’s owner, Sirio Maccioni, responded, “Sir, would you rather sit this close or this far from Sophia Loren tonight?—just as Sophia swept into the restaurant.

Of course, New York is the East Coast epicenter for celebrity dining. Some even own restaurants themselves, including Robert De Niro, who is a partner at Nobu with Harvey Keitel, Bill Murray, Mikhail Baryshnikov, Sean Penn, Ed Harris, Lou Diamond Philips and Christopher Walken. De Niro often brings his friends in to dine, so if that looks like Leonardo Di Caprio, it probably is.

The Waverly Inn, owned by Vanity Fair editor-in-chief Graydon Carter, is so exclusive that the restaurant doesn’t answer the phone; either you have Carter’s personal phone number, or you beg for a table in-person that afternoon. Once there, you may pass Uma Thurman and Anne Hathaway in the front room—on your way to Siberia in the back.

MORE FROM TRAVEL

Travel Section Front

World's sexiest islands 2008 Images: Home sweet home in America Good to go: Travel gifts for tight budgets How to — or avoid — getting bumped Miami hotel gets $1 billion makeover Chocolate lover’s paradises around the world Images: Floods in Venice The unfriendly skies: Best and worst of air travel No Who-ville in Louisville this Christmas Your turn! Travel to the Ends of the Earth Travel Section Front   Add Travel headlines to your news reader: