For a base tip, I usually figure leaving $1 for every $6 of the bill, rounded up.  So if  a bill is $15 for food and drink, I leave $3.  This comes to %16 to %23.  Then I may add or subtract a bit depending on how the service was.  If the server did a normal job, I won't add anything since what I'm leaving is usually a bit above the %15 anyway.  ( Read more... )