As Chris71 said, its good to invite them to something you are already going to. If there are other people that you know going too that is also good. That way it isn't as much of a "date." You could do a real date after that.
That being said, I wouldn't be too afraid to show interest. I think the little game of
does he like me or what ever is a pain, Don't tell her right off that you like her, you know that you like her body and her personality is of interest, but you can't be sure you like
her (atleast tell your self that
). If she is looking to find a partner and you are too, you don't need to play any elaborate games.
Its essential to understand that even if a girl is interested in you she will be leery to commit to going somewhere with you alone. She is in a vulnerable position as the weaker party. She needs to know that you are safe, something that cannot be assessed in a brief meeting, leading to her having to deny you when you ask her out.
Also, asking out a waitress is a whole other story as others have mentioned.
Good luck, I'm not an expert but thats my advice