In the US, service charges are usually not included in the bill. Waitresses and taxi cab drivers are usually tipped 15-20% of the bill. Some people also tip barbers and hair stylists a dollar or two. If you do not carry your own luggage, bellboys and porters receive $1.00 for each piece of luggage. No tips are given to theater ushers, airline personnel, gas station attendants, or "baggers" in grocery stores.