Cold approaches can be hard...
The reason why cold approaches are so difficult is not necessarily because of the ACTION of a cold approach - it is hard because most of us MAKE it that way. We believe that it is hard, so it will naturally be very difficult to us.
In reality, you already know what to say, it's just that you feel as if you aren't going to really be able to say it because you are so afraid of the end-result of what you are going to say, that you overthink the situation and become aware of what you think you don't know, thus stopping you in your tracks. Basically, you're doubting your own better judgment.
In fact, we've been knowing what to say since kindergarten!
Think about it, you made friends in kindergarten, right? Well....how did you meet them? That's right, you walked up to them, said "hi" and introduced yourself, and they responded and introduced themselves as well to you. How did you make friends in elementary school? The same way - you either walked up and introduced yourself to them, or they walked up and introduced themselves to you - anyway you slice it, somebody had to do the approaching, and somebody had to do the responding.
What makes this situation any different? Beautiful women are people too, and I'm pretty sure that most of them know how to meet people just like we all do. It's just that you doubt your own abilty to do so when you run across a hot woman because you feel that unless you do a damn good job, then she will not be attracted to you. We tend to get the impression that beautiful women see men as a dime-a-dozen.
I'm very successful with women, and I can tell you right now that I have a lot of extremely attractive women to choose from, because I can name you quite of few that wouldn't mind dating me. But I have never ONCE blown off a woman that was trying to pick me up that I didn't find physically attractive, EVER. The only times that I would blow them off was if they approached me badly.
In a nutshell, do what's been working for you your entire life - just walk up there and say, "Hey there, I'm (your name), what's your name?"
I tell ya right now, people just don't keep it simple like they used to!