Nearly 20 years ago, the humorist Dave Barry coined what’s known as the “waiter rule,” which is “if someone is nice to you but rude to the waiter, they are not a nice person.” It iis a simple fact of business that many CEOs and decision-makers judge the character of prospective employees and business partners based on how they treat servers.

Therefore, if you don’t want to come off like a jerk, you need to know the rule about tipping which is:

In a full-service restaurant in the United States, you are expected to tip a minimum of 15 percent, regardless of the quality of the service.

If you are tipping less than 15 percent, you are either ignorant, or you are being cheap and/or mean.

Being ignorant I can understand. My father, for example, was ignorant. He believed it was appropriate to leave a penny as a tip to punish a server for lousy service “because that way they know you just didn’t forget to leave a tip.”

While my father was a pastor and generally a kind man, he thought the “leave a penny” idea was clever and justifiable. Then he married my stepmother, who’d once worked as a waitress. She explained to him that servers must deal with customers who:

  • Leave without paying.
  • Let their children run wild.
  • Yell at them for chef’s mistakes.
  • Make inappropriate remarks.
  • Touch servers on their butts.
  • Send food back multiple times.
  • Claim they didn’t order what they ordered.
  • Try to bargain down the price of the food.
  • Talk so loudly that it bothers other diners.
  • Blow snot into the cloth napkins.

She also explained that servers must deal with employers who:

  • Force them to share their tips with management.
  • Schedule difficult hours making it hard to work another job.
  • Keep weekly hours at 30 or below to avoid offering insurance.
  • Expect unpaid overtime, especially in cleaning and closing.
  • Dock servers’ pay when their customers skip on the check.
  • Sexually harass servers, especially undocumented ones.

That’s a lot of guff to take for a job that requires you to be on your feet for hours at a time and which usually pays about minimum wage.

After my step-mother explained this, my father was no longer ignorant. From that moment on he tipped at least 15 percent, regardless of the quality of the service.

Over the years, I’ve heard plenty of excuses for under-tipping. Here are the most common justifications, along with an explanation of why they’re bogus:

  1. “Servers should be paid more rather than be forced depend upon tips.”
    Answer: they aren’t being paid more and they do depend upon tips. Regardless of whether that’s how it should be, that’s the way it is.
  2. “If the server isn’t doing the job well, I shouldn’t have to pay for it.”
    Answer: If the food arrived at your table, the server did the job and deserves to be paid.
  3. “I’m helping the server improve by pointing out poor performance.”
    Answer: if you wanted to help the server’s performance, you’d give some professional feedback, not stiff them on the tip.
  4. “Why should I tip? I don’t get a tip when I do my job!”
    Answer: that’s because you aren’t a server and your compensation isn’t dependent upon tips. There’s no basis for comparison.
  5. “I paid good money to eat here. Why should I pay more?”
    Answer: because tipping 15 percent (minimum) is part of the social contract of eating in a restaurant.
  6. “I was treated badly, so why should I be magnanimous?”
    Answer: tipping 15 percent isn’t being magnanimous; it’s tipping the bare minimum.
  7. “Tipping is optional, so I can tip whatever I want.”
    Answer: You can also walk around wearing a T-shirt with obscenities on it. Like under-tipping, doing so marks you as a jackass.
  8. “If there’s no threat of a low (or no) tip, I won’t get good service.”
    Answer: Trust me, there are enough jackasses out there that the threat of under-tipping is always present.
  9. “If I don’t tip this time, I’ll get better service next time.”
    Answer: you’ve got it exactly backwards. Once you’re known as a low tipper, you’ll get poor service.
  10. “I always get lousy service so I simply must do something.”
    Answer: You’re getting lousy service because servers are good at reading people and they can tell you’re a low tipper.

Now that you know the facts, you’re no longer ignorant, so if you continue to under-tip, you’re either cheap or mean.

More than that, you’re being stupid, because your violation of the “waiter rule” is telling all colleagues, customers, employees and business partners that you’re either a cheapskate or a jackass. And that’s definitely going to hurt your personal brand.

One last word of advice. If you really do want great service, give the server a tip the moment you’re seated and say: “that’s not the tip; it’s just a little extra because I know you’re going to take good care of us.”

Works every time.

The opinions expressed here by Inc.com columnists are their own, not those of Inc.com.