A friend in town from New York this weekend told a story of getting terrible service at a restaurant while dining with a handful of guys. Once the check arrived, one said he didn't want to leave the server a tip. The table argued. "He got his drinks. He got food. The waitress may have been rude, but she still deserved to get paid," said my friend. "This guy wanted to give the tip right to the busser to emphasize to the waitress how much the service sucked." 

Tip 20 percent. Every time. Pre-tax? Post-tax? In practice the difference is no more than a buck or two, unless you're Joe Pytka. In which case there's a $10,000 wine tab, so it works out. But the idea that a tip is optional, or variable, is a useful fiction, even when the soup goes tumbling into your lap. The owner gets to pretend her prices are lower, the busboy makes rent, and you get to feel like a philanthropist. A win-win for all. 

Yes, I know your parents still talk about when the recommended percentage used to be 15 percent, and that the practice is considered barbaric in Japan. But it's not 1973, and you're probably not in Osaka at the moment. 20 percent. 

Gold suggests a 20 percent tip on the price of wine, for the delivery guy, when the owner takes care of the table, and at the bar-whether it's booze or coffee. The variations are for a pick-up (10 percent) or the parking attendant (varies). 

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