I don't know about you, but when I am abroad I never really know if I should tip or if I shouldn't. In the United States it seems like you tip for every. single. thing. that happens. You hauled my bags in and out of your taxi, well that's $2 a bag. And I took your taxi, so that's another 20%. Oh, you hailed a taxi for me? That's at least $1. Everything is tippable. Everything.
But how much? For what services? When you are not in the States what do you do? Well, I finally found a great article that gives a brief overview of major tourist destinations and what to tip. Read it, commit to memory and have a great time!
Tip: A couple of weeks ago, a friend of mine who consistently frequents tippable hotels says that she takes a "Tip Wallet" this wallet is full of ones and she takes it out when there is a tippable moment. Bell Man gets your bags? Cleaning lady does an excellent job? Taxi driver gets you there extra fast? Grab your Tip Wallet and use those dollars!