Your Philosophy of Tipping

Certain recent events have convinced me that I've been tipping too much too soon and for too little. And unfortunately in the majority of cases, my generosity is not leading to improved results. In fact, my mileage is actually decreasing -- more often than not -- with the women I try to make my regulars. I don't know if I should just not tip, just not repeat, or only tip if my mileage improves. What do you guys think?