I have never been rejected by the opposite sex
In my experience the trick to never being rejected is to never make it obvious that you are only after one thing. Which is easier to do if you aren't only after one thing. Except in a few instances, girls rarely like having to make a decision about you there and then, so don't force one or the default answer will be given. Which is no.
And frankly, I don't like having to make a decision there and then either, because I am quite like a girl in that I don't know if I want to be with that person until I've got to know them a little, even if they looked like Angelina Jolie and I only wanted to have a one-night stand. They still have the ability to misinterpret me and insult me as a result in way that makes me feel terrible and hate the world for a few days.
So I just look to chat with them as if I was chatting to a guy, but with a little more eye contact because its nice looking at a pretty girl's face if nothing else. And I enjoy the experience for what it is, if they then disappear so be it, if they bundle me in the back of a taxi (never happened) so be it. 6 months later the same girl will come over and say hello in another bar....