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: