Figuring out tipping practices both at home and when traveling abroad can be a major headache. Some travel companies now include all tips in their set price which is a blessing. But if they do not, they usually provide some guidance on what would be an appropriate gratuity by the type of service provided. But if you're on your own - here's some guidance that might help:
Don't tip in Japan and China. Think about it in Switzerland and Sweden. The decision will be made for you in France, Italy, Germany, Austria, Hong Kong, and Singapore in which a service charge is automatically included, but you can round the bill up if you want to leave extra for your waiter.
In London, a discretionary 12.5 percent tip is often added to your bill. It's probably just as well – you try working out 12.5 percent of 150 quid after a couple pints – but some staff will also leave the tip column open on your credit card receipt, hoping you will tip twice. If in doubt, there's nothing wrong with politely asking if service has been included.
As well as these other helpful sites:
The rules of tipping aboard ships varies from company to company and among the various forms of sea/river travel. Check with your booking agent or the ship line directly to determine what extra cash or credit card balance you will be expending on this extra expense of your trip.