Translation:
Boy: Hello there, attractive looking potential mate; I couldn't help but notice you.
Poster: Pardon my confusion, but is it to me that you are referring?
Boy: Yes, I was referring to you. I find you to be rather attractive, as demonstrated by the fact that I have publicly approached you, risking the threat of rejection and the mockery of my peers.
Poster: Is that so?
Boy: Indeed it is. In fact, I think that we should share contact information so that I can get to know you better/solicit you repeatedly for sex.
It got a good chuckle out of that
Anyway, on topic: It's always a difficult predicament. They say that you're more likely to meet a long term partner outside of the clubbing/bar/partying scene when you're not expecting it, yet when are you allowed to approach these people. Maybe in Britain we are scared of bothering or hassling someone? If I were an attractive woman (not a start to a sentence I have used before), I'd get sick of guys bothering me.
I guess you need to keep it light-hearted and not come across as looking for one thing and one thing only. Look for boyfriends/wedding rings before you go anywhere. Smile, laugh and make light of things - look for something in common and allow her to interpret it how she wants. If she's not interested, it's just polite conversation and a quick smile between strangers. If it feels like there could be the opportunity for something more, use your charm. Eye contact is always a good first step - just walking up to someone before they have even acknowledged you is not always advisable - try to give her a reason to acknowledge you therefore. But then some women like a direct, confident approach ...