Often without consistency, service charges of 10% to 15% may be added to hotel and restaurant bills. Especially in restaurants, be sure to ask if a tip is included; that way, you're not either double tipping or short-changing the staff. Taxi drivers, porters, chambermaids, and restaurant waitstaff depend on tips. The guideline is 10% to 15% for waitstaff and cabbies, $1 per bag for porters, and $1 to $5 per night for chambermaids.