The current understanding of the practice of “tipping” apparently arose in England around the 17th century, when it expanded from a gratuity provided to servants when staying at a private home to become common in numerous businesses. While the practice is very common in the States and in many other countries, travelers should prepare themselves to adjust to different tipping customs before going abroad.
First, remember that tips are important in the cultures and countries where they are prevalent. One study pegs the size of the “tipping economy” at some 40 billion dollars, and in parts of the world where tipping is common, it can make up a large part of the wages of service workers. Likewise, people in the countries in which tips are undesired can take considerable umbrage at the suggestion.
Tipping is more or less endemic throughout North and South America, though on the latter continent, one should expect to only tell taxi drivers to keep the change. European countries tend to lean one way or another. Look up this information ahead of time, because the proper amount to leave can vary across the continent (though tends to be somewhat lower than in the US) and many countries are trending toward including service charges in the bill. The Middle East and Africa also like their tips, but as you head further east, tipping culture begins to wane. Indians generally have no expectation of extravagant tips, and both the Japanese and Chinese regard tipping as somewhat taboo. Likewise, Australia and New Zealand are not huge tippers. It is generally worth noting that major cities generally expect a bit more, while rural areas expect less. However, be sure to research your specific destination ahead of time for the finer points, as many countries’ hotel staff expect tips while restaurants and taxi drivers do not.