http://sg.finance.yahoo.com/news/ultimate-tipping-guide-163415620.html

What you think about tipping probably depends on your viewpoint on the world - whether you've worked in a service job that only paid well if you received tips, whether you have a lot of money, whether you don't. You may tip out of due diligence, but get no pleasure or pain from it. You may loathe the very concept of paying extra for a service and never tip. Or you may feel good about tipping, and see it as a way to pay it forward and keep the economy's engine humming http://sg.finance.yahoo.com/news/ultimate-tipping-guide-163415620.html