Here's the scenario:
1) You went to a fancy restaurant and ended up with a bill of $250. Your server was excellent, service was great, and prompt. How much do you tip?
2) You went to the same fancy restaurant, and got the same bill. Service sucked, the waitress screwed up six times, and it took forever to get your food. How much do you tip?
3) A bellman brings up your luggage form your vehicle, explains the hotel and how everything works, gets you ice, and more coffee. You had six bags, and there are three of you. How much do you tip?
4) You order pizza. The total comes to $25. You have it delivered. It's delivered on time. How much do you tip?