O/T Flirting, how do you know?

I am working on trying it right now. I am trying to get this guy I see fairly often to realize I am interested in him. I'm using these flirting tips along with the theory in the book Stop Getting Dumped. I think I might end up with some outside help though, his sister ended up finding out I am interested.

As a guy who has been married 14 years, I must say that I flirt constantly.  I know nothing will come of it and frankly, I like it that way.  But the tension involved in flirting is something that I really enjoy. I say, if you like it, do it.  If you don't, say you don't like it. If you show interest in someone they might show interest in you.  If all they want is sex that will become pretty obvious very quickly.  The object of the flirt is to create tension and interest.  An emotional chess match.  If it good, you both win.  If it is bad, you just play with someone else.