^ Despite your joking recently this did actually happen to me (I never normally meet people like this :p).
A friend and his gf decided to try and set me up with a mutual friend, started with a friend request and although setting us up didn't work, we've actually become really close. Normally I get friends with people through work.
They start with a simple smile, a curious question for the companion and followed by a convivial introduction. I find that the best ways to make friends is when you talk less about you and ask more about them.
I recommend reading "How to Win Friends and Influence People" by Dale Carnegie. A worthy read!