Tipping customs for cab drivers vary from country to country and even from city to city. Fifteen to 20 percent of your fare is a good rule of thumb, but you can tip more or less depending on your experience. Check with the locals when you arrive at your destination to determine what you should consider when tipping your cab driver.

Area Knowledge

A good cab driver will have a strong, thorough knowledge of the area in which he works. He should not have to ask for directions if you provide a street address. If he does ask, he should do so no more than once. If you ask for advice on where to go in his city, the driver should be able to suggest a few popular attractions without much effort. He should also be aware of alternate routes in case of a traffic jam or accident that obscures the road.

Speed of Service

Cab drivers cannot help traffic jams, but they can choose the most efficient route and take steps to decrease driving time. Feel free to tip low if your cab driver dawdles or takes an unnecessarily circuitous route. Reward your driver with a few extra dollars if he makes record time or manages to avoid an accident or traffic problem. Time is money -- when a cab driver reduces your time in the cab, he's also reducing your total fare. Make up the difference when you tip.

Extras

All cab drivers should offer to help with baggage; if yours doesn't, don't feel obligated to tip above and beyond the norm. Utilize your driver's local status to get more out of your trip, such as asking him to indicate points of interest throughout the trip. Don't punish your driver if he's too busy driving to play tour guide, however. Tip more if he gives you insider advice, such as where to go for extra-cheap drinks or the best time to see a particularly popular place.

Demeanor

Cab drivers deal with dozens of strangers every day and many have become inured to the whole process. If your cab driver is friendly, helpful and doesn't mind chatting, reward him with a better tip. If he talks on a cell phone throughout the trip, is verbally abrasive to other drivers, drives recklessly or cuts you short when you ask questions, don't tip more than 15 or 20 percent. Don't hesitate to get out before your destination and refuse to pay either fare or tip if you feel the driver's behavior or driving warrants it.