Yesterday, net-bouncing brought me to this tipping guide. It's pretty good... however... I live in the midwest. Here at the home of the Gateway Arch, cab drivers do not open your door or get your luggage. They pull up near your house and honk. Why should I tip them? What personal service has my cabbie provided?
On the flip side, when I go to a coffee house and ask for a mocha cappucchino with an extra shot, (and I mean cappucchino, not latte, I want foam in my cup stiff enough to hold a spoon) I tip generously. Yes, I'm only requesting that the barista do their job properly, but it seems like St. Louis baristas can't get a grip on 'mocha' and 'cappucchino' together as a drink. They just assume I meant latte, and I don't know what I'm talking about. I would ask for something even weirder, like english toffee and bananna, but I've just kinda lost my faith here.
I'm a nice person, so my order usually goes like this- "Can I get a mocha, but as a cappucchino? With an extra shot please? I really love foam." They'll make my drink and ask, "Ya want whipped cream on top?" (of the latte they just made for me) Thank you, no. I just want a buttload of foam. I don't need 2 tons of milk to water down my espresso with. If it were up to me, I'd mix the chocolate right in with the espresso and just pile on the froth on top. That's really all the milk I want.
I loved working as a barista at The Mudd Room. I could make my espresso any way I wanted. I'm still trying to save up for a real espresso machine for my home.

My pre-rant point was this- When someone gives you a personal service, or goes above and beyond their standard duties in servicing your request, you tip them. When a cab driver honks for you 3 houses away, you stiff him/her.