This is always a problem that the 2 sexes have. One sex puts the other on such a high pedestal and makes it impossible to talk to one another. Just realize you're talking to a fellow human being. The worst that can happen is that they're not interested. No biggie. Go out and try it, I guarantee you'll be just fine.
I'm trans and intersex so I can't approach men. It could turn violent for me. However if you're just a cis girl I feel like just going up to a guy and being honest would work.
Guys are just people, just treat them as you would anyone else. Don't think about "how can I talk to him so he will go out with me" as that puts pressure on yourself. Just start building some rapport with a guy (or anyone) who looks interesting to talk to. A tip my mother once gave me that I still use today is to ask him questions about things he is interested in. People love talking about themselves, especially guys. If it is a topic you don't know about then use him as an opportunity to learn more about it by asking him questions. You can also use absolutely anything to break the ice; eg. you are in a shop waiting in a cue and you are standing near a guy who appears to be on his own you can say "gosh it's busy in here" and that can lead to a conversation.