Service is not included in restaurants and it is customary to add a 15% tip to the total. (A quick way to calculate the appropriate tip amount is to add the two taxes that appear at the bottom of your bill. It works out to roughly 15%).
If you are with a group, 15% for service may be automatically added to your bill. Just ask when you are not sure if tip is included.
Taxi drivers, hairdressers, etc. are also normally tipped 15%.
Bellhops, porters, doormen, etc. generally receive at least $1 per suitcase or per service rendered. Coffee and food counters often have a tip cup next to the cash register; spare change is always appreciated.