Where can I find information about tipping etiquette in different countries? I'm hoping for a comprehensive database so I don't have to ask about the countries one by one here.
Here's a pretty good compile list of different countries. It obviously doesn't have every country but it should get you started...
For anyone coming from a country where tipping isn't a big thing, I'd suggest this humorous article from a BBC correspondent for an explanation of why it's important in the states, and how it changes things.
Personally, I either check a guide book on the country I'm going to (they usually give some helpful advice in the general section), or failing that just ask. I've generally found staff to be very helpful when it comes to explaining the tipping norms to tourists! Even better is to ask a friend in the country, or maybe just the local sat next to you on the bus/plane/train.
Daily Infographic has created a visual guide to tipping customs around the world. Doesn't cover every country in the world, but from what I see the countries that I have visited it seems about right. The infographic also mentions tipping customs outside the food & beverage industry, that can be useful to avoid faux pas.