tipping on a night out on the town

so going out to dinner and waiting for the services and seeing how it is presented. the thing is put yourself in the server's shoes and knowing the taxes and things that go down and knowing that not much actual money is made per hour as to per customer. so what is the fair amount to give? what do you feel is the actual value for services of extra food, personality, and overall good natured skills?? I have had some good to great hostess over the years and then I have had Poor to horrible servers and some ok ones as well. now come tip time expressions and exchanges become interesting. I will tip beyond the norm with great service as was the case on a recent night out. but i have also dropped basic coins on Poor services. the quality of service sometimes overrides the actual meal. a Good Meal is good and important,but quality services brings you back and you will tell people you are cool with.customer service goes a long way.