How do you get a girl/boy to like you?

What do you usually do when you like someone and you are desperate in having her/him. I usually do what comes in my mind go to her and speak open not using old lines from bad movies or pretending to be something that I'm not. When I like a girl I go and do what my heart tells me to do. But now I don't have to use any lines in getting a girl to like me because I already have a girlfriend for 2 years now. I went to her talked to her and never felt any better than talking to her.