It’s not a definitive guide to tipping etiquette around the world, but its a start. It even covers what to do here in America, where we easily put other tippers to shame.
Generally, expect to tip in North America for most things. With a few exceptions, Australasia generally doesn’t tip. It also seems like some parts of Europe tip, while others don’t; I generally assume its included unless the website formerly known as Wikitravel says otherwise.
If you end up getting above-and-beyond service anywhere, tipping should probably follow no matter where you are. (It’s called human decency.) Hopefully, I’ll end up covering tipping more in-depth some time later on in the game, but this will have to suffice in the meantime!