This one can be the hardest to follow, but abide by it. Girls know within the first 5 minutes how far they will go with you, and will probably do so at the earliest possible time. If you've been crossed off the "I'll sleep with him" list, it's very very difficult, and time consuming to get back on it.
Your time is better spent chasing new prospects. If you're on the list, you can still screw it up by being a jackass. If nothing's happened in 3 dates, it's time to move on. The chances of you sleeping with her by now is very low. The only time you should see her again is if there is guaranteed sex. Continuing to pursue her will just cost you more money and waste more of your time.