The customary tipping rate is 15%-20% for taxi drivers and waiters; bellhops are usually given $2 per bag in luxury hotels, $1 per bag elsewhere. Hotel maids should be tipped $2 per day of your stay.
A doorman who hails or helps you into a cab can be tipped $1-$2. You should also tip your hotel concierge for services rendered; the size of the tip depends on the difficulty of your request, as well as the quality of the concierge’s work. For an ordinary dinner reservation or tour arrangements, $3-$5 should do; if the concierge scores seats at a popular restaurant or show or performs unusual services (getting your laptop repaired, finding a good allergist, etc.), $10 or more is appropriate.
Waiters should be tipped 15%-20%, though at higher-end restaurants, a solid 20% is more the norm. Many restaurants add a gratuity to the bill for parties of six or more. Ask what the percentage is if the menu or bill doesn’t state it.
Tip $1 per drink you order at the bar, though if at an upscale establishment, those $15 martinis might warrant a $2 tip.