^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.^