I've a friend who is great at approaching people. I guess she is a natural. I think it is not just about approaching. For that asking someone to take a group picture might work. I think it is about "reading clues" about what to speak or comment. She can take a look at the guys clothes and identify conversation topics.

But I think that when the other person is interested, it would make it easier for you. Women do that too. If they guy seems interesting, even if the approach is not the best, you'll smile and speak to him. Unless he is rude or an idiot.

I think that the real problem is not about "skills", but about accepting the posibility that the person you approach might or might not be interested before you approach an open your mouth. I mean, if the woman has a partner, she might not be interested regardless what you say or do. Or if she is simply not attracted for whatever reason. Same with men.

Flirting is a two way thing. Some people find "cute" that the guy is shy or clumsy because they like the guy and that's it. And they can find that a guy with "game" is arrogant even if he has a flawless delivery. Attraction is complex and not necesarily about skills or techniques.