You reap what you sow

I got a credit card slip once that looked like this:
Amount Due: $27.58
Tip: $0.00
Total: $27.58

I brought you refills when your glasses were half empty, I put your order in the computer correctly, and I made sure you had everything you needed, including extra Sweet N Low and salsa. I apologized when you informed me (after eating half of it) that your quesadilla came out with onions in it. I did tell the kitchen staff to leave those off, but they may have had a mix-up or been overloaded and simply overlooked the note. It was not my fault, but I did offer to have the kitchen remake your food. All I can do is apologize to you and offer to fix the problem. If you refuse to allow me to help you, it then becomes your problem, not mine. I do not have the authority to comp your meal unless you allow me or a manager to fix it, so do not be angry when you expect to be compensated for a problem you refuse to allow us to rectify.
Also...you are supposed to tip on service, not on the food. I did everything I could to provide good service, therefore I should have received a tip.

People, come on. If your order doesn't arrive at your table the way you want it, for God's sake let your server know and let them fix it for you! That's what we are there for - to help YOU.
Realistically, you will probably never know for certain if the error was the server's fault or the kitchen's fault, but that's okay - mistakes happen. We use computers to communicate with the kitchen, which aren't perfect. We're likely juggling a dozen other tasks which we must also prioritize. That also goes for the kitchen staff. So chill out a bit and acknowledge that people aren't perfect and we have feelings, too. Show courtesy to us and you will receive the same. I am more than happy to help you regardless, but when you are polite and understanding, I will go out of my way to make sure you have a great dinner.