Check the local customs. Tipping in different countries can varying wildly from being not common at all (Japan) to being a worker's primary income source (Mexico). If you have access to a good guide book, it should list common tipping practices for the destination you wish to visit.
Keep small bills and change on hand. An employee shouldn't have to miss out on a tip because you only have large bills. Keep in mind that in many poor countries, it can be hard to make change for large bills unless you are at a bank or large store. Keep a small change purse or section of your wallet free for change and small bills.
Tip the people who help you. If you use a porter at the airport, tip him per bag. Same with the bellhop at the hotel. One dollar per bag is standard. While you may not see your maid at the hotel very much, you can be sure that she works hard to keep your room clean and many people can be extra messy on vacation! It is standard to tip your maid $5 per night that you stay. In many countries, you are not expected to tip cab drivers unless they help you with your bags.
Ask about special circumstances. In Mexico, for example, it is customary to tip gas station attendants and baggers at the supermarket. In fact, the baggers are often school children or the elderly and they do not make wages, only tips. Ask the concierge at your hotel for special circumstances in the country where you are visiting.
Calculate a percentage. For restaurants and tours, it is best to calculate a percentage of the total price before taxes. In a restaurant, tipping between 10-20% is standard, but ,especially if dining in a poor country or if the restaurant prices are more than reasonable, tipping extra could mean a huge difference to the employees. Also, in many places tips are pooled, so your waiter will have to divide his or her tips with the bussers, dishwashers, chef and host. For tours, it is customary to tip both the host and the driver/captain. Ten percent of the tour price is standard.
