When do Canadians and Americans usually tip? They tip when they ___________________the service.

Canadians and Americans usually tip in places like restaurants, airports, hotels, and hair salons because many people who work in these places get low salaries. A tip shows that the customer is pleased with the service.
   At airports, porters usually get a dollar tip for each bag. Hotel boys get a dollar for carrying one or two suitcases. Many people also tip hotel room attendants, especially when they stay in a hotel for several days. They usually leave a dollar each day.
    The usual tip for other kinds of services--for example, for taxi drivers, barbers, hairdressers, waiters and waitresses--is 10% of the bill. The size of the tip depends on how pleased the customer is. In most restaurants, the check does not include a service charge. There is no tipping in coffee houses or fast-food restaurants.
11. When do Canadians and Americans usually tip?