Don't go out with girls that have been with your friends without talking to them about it first. EVER.
I let you imagine how that rule applies if said friend is still with her. Good thing you gave up.
Yeah, dating/social networking sites are good. Just try, you'll come off weird at first, but whatever. You'll improve that way. Also don't hesitate to ask women on said site on how to improve your talking to them - seriously! Do it.