In my neck of the woods, servers make $12/hour. Before tips, because LA no longer lets restaurants rely on tips for wages. (And that's increasing to $15/hour by 2020). So unless service is really good, I default to 10%.
And quite frankly, it's disgusting that the person who spends may 30 seconds providing service gets X% of the bill when 99% of the work is done in the kitchen by guys who don't get paid anything extra.