A friendly and proficient taxi driver can greatly enhance your ride, just as grumpy cabbie with questionable driving skills can make the drive a nightmare. In either case, the tip you give upon reaching your destination is a way to show the driver what you thought of his service. In general, the tip should be a percentage of the cost of your trip, with a few extra bucks added for helping you with your luggage, if applicable.

How Much to Tip

The Emily Post Institute, a nationally recognized etiquette organization, recommends tipping your taxi driver between 15 and 20 percent of the total trip fare. As you approach your destination, check the cab's meter and make a quick calculation in your head or with the calculator app on your smartphone. If you've traveled with luggage and your driver has helped you, it's proper etiquette to tip more. The general rule is $2 for the first bag and $1 per subsequent bag.

Influencing Factors

Although your tip should typically be between 15 and 20 percent, a variety of factors can influence exactly how much you give. Give on the upper end of this range, or even above 20 percent, if the driver gave exemplary service -- for example, if he drove quickly but safely, offered friendly banter or provided some details about a city you're visiting. You don't have to leave a tip if the driver is unfriendly or drives in an unsafe manner. Additionally, take down the cab company's phone number and the driver's number and report him.

How to Tip

It's a smart idea to always carry some cash when you plan to travel by taxi. Cash is a simple, straightforward method of tipping. Many taxi companies allow you to add a tip to your debit or credit card bill, just as you might at a restaurant. Occasionally, however, you'll encounter an unscrupulous driver who insists that you pay by cash. To cover your bases, call the cab company before your trip and ensure you can pay and tip with your card.

Traveling Abroad

Taking a taxi while traveling abroad requires a slightly different approach. The tipping expectations in each part of the world vary greatly; in some countries, 10 percent is appropriate, while in others, $1 is acceptable. In many European nations, such as Spain and Greece, you can simply round up your fare to the nearest dollar. To avoid being exploited financially, check with the cab company about how much a trip to your destination will cost. Many airports also sell tourist guides that explain tipping customs in the country.