You assume I don't know the interior world of the introvert. That is a pretty big assumption and wrong. For me, I didn't try and chat someone up. The key was to treat the opposite sex as people. If you are freaking out not knowing what to say, how about asking them questions? When they talk, then listen. People you will think you are a brilliant conversationalist if you talk about them. They will probably give you clues as to the next thing you might want to say or ask. So to address the last line of your post, I didn't start of talking. I started off listening.
As for how you get interested, well either you do or you don't. Once again, listen. Are they interesting, caring, funny, deeply invested in their relationship with God? All of these things lead to discussion. Don't try and manufacture the conversation in your head before you have it.
As for the prescreening, it helps if they are known to your friends or family or one of your networks. It is hard to prescreen for manipulative personalities. You can't protect yourself with a 100% guarantee. People don't work that way, but it isn't "men are this alien species that can't be trusted." You kill it right there if you approach people in full armor. The other person is scared too.
As for the best foot, it is the one that doesn't kick your past laundry all over some unsuspecting guy and then have you follow up with "This is who I am so take me or leave me. I don't care. As a matter of fact, hand me back those knickers."

Seriously though, all people just want to be seen for themselves.