For people traveling to a new destination it is quite common not be fully aware of the local customs and cultural differences in many situations.
In many parts of North America, a 15 to 20 per cent extra is expected in restaurants and porters carrying your baggage expect one or two dollars per bag, depending on an accommodation category. However, travelers to Japan and China aren't expected to tip services provided. Gratuities might be even extremely costly to some workers in China, since accepting tips can be even cause for being fired.
Tourism Review brings a Tipping Guide Infographic for better understanding of tipping cultures around the world:
http://www.tourism-review.com/infographics/tipping_culture.jpg
South Africa is missing from the list. Generally a tip of around 10-15% is customary at restaurants for good service. Waiters get paid very poorly and rely on tipping to make a living. Tour guides and safari guides also expect a decent tip for good service, as they earn very low wages. About $10 (R100) per day is average. Hotel staff also appreciate tips - from porters to house keeping. Again, these people earn minimum wage so any tip will be very welcome. We have a more detailed blog post about tipping on African safaris on our website.
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Kilimanjaro guides and porters also expect tips to compensate for the high services and low wages they receive. $5 per day per porter, $10 per day per guide are standard and well-deserved. Safari and other guides receive tips as well. Most tourist lodges have tip boxes where you are expected to contribute some amount to be shared among all the staff.