Still I do understand how you feel, I am going to be thirty this year and being a guy I didn't give much thought to this matter when I was a kid but I always just assumed by the time I was this age I would be a world famous writer and be married with a kid or two. So I am kind of depressed right now.
Still thinks are getting better and as I said they are much better then they were when I was a teenager. If you are interested in a girl just go up and talk to her like you would anyone else about something you have in common and no matter how nervous you are don't show it. That tactic has worked wonders for me.
Hope things get better for you.