Visitors to Nigeria often end up exasperated by a culture of bribery, extortion and petty theft that can make even the simplest itinerary a challenge. Ominous-looking roadblocks can pop up anywhere and anytime in this kleptocratic environment, and it may take a small bundle of cash to get through. Yellow Lagos taxis are cheap and plentiful, but proceed at your own risk.

Tip: Work with your hotel concierge to find private transportation and stress-free routes.

In the country that gave us Ferraris and Lamborghinis, aggressive driving is a given, and nowhere does it get crazier than in Naples, where your taxi driver may simply take to the sidewalks if he finds the streets too crowded. It's the kind of place where "one way" really means "my way," whatever your way happens to be at that moment. And when you step out of the cab, keep an eye out for motorcycle-riding purse snatchers who'll think nothing of snapping your wrist to grab your Birkin bag.

Tip: Go private with Benvenuto Limos, or forget the whole thing and take a fast boat to Capri.

For more information: Benvenuto Limos

As is the case in many cities worldwide, Caracas's white taxis are supplemented by an unregulated and un-insured fleet of unmarked pirate taxis which may identify themselves to you simply by flashing a paper sign that says "Taxi." Don't get in. You'd be better off strapping on a helmet and hopping on the back of a motorcycle taxi for a true Venezuelan thrill.

Tip: Check with your hotel for private cars, or stick to telephone taxi services such as the well-regarded Taxi Capital.

The new Russia's anything-goes form of capitalism carries right over into the world of taxis. Indeed, anything goes, and anyone will pick you up if you stick out your hand. You'll see plenty of metered yellow taxis, but you'll also attract gypsy cabs—ordinary Muscovites who are simply looking to make a few extra rubles as they drive across town. If you don't speak Russian, you may find it hard to haggle and could end up getting into an incomprehensible shouting match.

Tip: Book your trip in advance online at sites like Way to Russia, which offers services around $16 per hour, or www.limos.ru, which can provide a Czar-like ride in a Hummer.

For more information: Way to Russia

A megalopolis of almost 30 million people (and growing), this Brazilian behemoth can be nearly impossible to get around at times of peak traffic congestion. Think of Los Angeles, only three times as big and crowded. The city's white taxis are plentiful and efficient, but given the distances and the traffic, you could be in for a very long ride. Plan in advance for off-peak trips with Rádio Táxi Vermelho e Branco.

Tip: Do what the rich locals do, and stay above it all by taking to the air. Sao Paulo has helicopters and helipads galore, making it possible to hopscotch from airport to hotel to meeting without ever setting foot on the street—very Blade Runner. Investigate the high life with ATM Helicopteros.

For more information: ATM Helicopteros

Those green-and-white VW Beetles may be among the world's cutest taxis, but sad to say, Mexico City is home of the "express kidnapping," during which a taxi-driving thief might take you to an ATM, rough you up, and force you to withdraw money. The problem is so well known that the Department of State maintains a travel warning about it.

Tip: Only take taxis that you've contacted in advance or that you hail at a regulated taxi stand, called a "sitio."

The 7.5-mile Qadisiyah Expressway from Baghdad International Airport to the Green Zone, sometimes referred to as "Route Irish" by American military forces, currently holds the title of the world's most dangerous road. Taxis do exist in Baghdad, but few drivers will make this trip unless they really need the money. Well-heeled visitors (mostly journalists) have been known to pay more than $5,000 for a small armored convoy complete with four gun-toting bodyguards.

Tip: Stay in Jordan.

The problem in Bangkok isn't with its colorful fleet of air-conditioned taxis and friendly drivers. The problem is how many of them there are, not to mention all the other cars, trucks, and buses clogging the narrow streets. Add the iconic three-wheeled tuk-tuks darting around all the other vehicles, and you have traffic chaos that will require true Buddhist detachment to endure.

Tip: Take to the water. Do your northbound and southbound traveling in a hired boat on the Chao Praya River. It's fast, scenic, and not outrageously expensive.

In a city full of fanciful transportation alternatives--everything from rickshaws to wildly decorated jeepneys--the local white taxis appear boring by comparision. What won't be boring is the fight you have with the driver when he refuses to turn on the meter (frequent visitors say it happens all the time) and instead tries to haggle for an unfair flat fee. Ask that he turn on the meter before you close the door and sit down. If he won't, simply flag down another taxi and try again.

Tip: Hire a private car (as low as $20 per day), or try the reputable Avis Taxi (011-63-2-532-5758), which comes when you call and adds about 70 cents to the meter for the pick-up.

Cab rides in New York can be glorious on a summer day in Central Park, or... the worst. Sure, things have picked up since the fictional Travis Bickle, played by Robert De Niro in "Taxi Driver," was at the wheel. But the Big Apple can still be notoriously unfriendly to visitors arriving by air. After their customs ordeal, travelers cabbing in from JFK will encounter gridlock on the notorious Van Wyck Expressway, a six-mile stretch of nightmarish congestion, plus the language barrier between passenger and driver (cabbies in New York are generally averse to English). Luckily, it's a flat $45 fare, so no matter how long you sit (and sit), you won't pay more.

Tip: Make the trip by helicopter in 8 minutes for $140 with U.S. Helicopter

For more information: U.S. Helicopter