I tip pretty decent, only because I know that importance of it from the recipient point of view. I used to park cars, valet .. and was getting minimum hourly rate and was working for tips, mainly.
To my hairdresser, I pay about 33 percent (they charge $15, I give them 20 dollar bill). in restaurants, I always round off the figure to next 10 or 15 .. so if the bill is $33.23 .. my tip would be such that my total will become $40.00. Higher the bill, bigger the rounding off would be in my case.