You just start a conversation about anything. I like making jokes and casual smiling. Then eventually say something like you want to exchange numbers and go out sometime. Or you can become friends with them, and just get the number and hang out sometimes, and not actually date. I kinda like this way better, don't have to pay for food...just beer if you hang with them at your house or theirs. But that's me, being hesitant of relationships. I have girls where I've been friends with and hang out like friends do, but we have never friendzoned each other or anything.