The art of tipping is one that few Americans know. There are many different opinions on what tips are expected, how much to tip, and who to tip. Some say an appropriate tip is 15% across the board, while others say 20%, or more, depending on the service provided.
Tipping is a way to provide an incentive for good service.
In general, this is how people tip at a restaurant: about 20%-15% for an excellent service, 10% for a good service, and 5% for a bad service.
Tipping is customary in the United States and Canada as an expression of gratitude and acknowledgment of excellent service. In some cases, it may be considered rude not to tip unless the person doesn't have enough money to do so.