HOW TO TIP AT RESTAURANTS/DINERS IN THE USA:

  Ken's Rules: Let's say your bill is $18.37. Now the typical
  range of tipping is between 10% (poor service) to 20% (excellent
  service).

  How much do you tip? 18% is what they prefer.

  Guess what? Don't get confused by those numbers

  DON'T BE CHEAP:

  DO THIS:

  Round $18.37 up to $20.00

  10% is simply the decimal point moved to the left.

  So 10% of $20.00 is $2

  Double it to $4.00, which is 20% of $20.00

  $20+4 = $24.00

  Yes, that's more than 20%. So what? Make $23 or even $22 if you
  like. You're still tipping a fair amount and you didn't have to
  get a calculator or hurt your brain figuring out PENNIES. Let
  the pennies go.

  And next time you go to the SAME restaurant, there's a good
  chance you'll get slightly better service than people who tip
  less. Certainly worth a few pennies or a dollar. Don't be cheap.
  They work hard.