My advice would be to talk to girls the same way you would talk to your guy friends. I'm a girl around your age and I find it really cheesy when guys use pick up lines or even when it's really obvious that they're hitting on me.

Take this one step at a time. First make friendships with females, treat them like a friend and nothing more. Once you're comfortable in the friendship (but dont wait toooo long because you don't want to get stuck in the friendship zone) start making it a bit more obvious that you're interested in more than friendship, try complimenting her and light/fun flirting. If she seems into that then maybe ask her to hang out, like renting a movie, going for coffee, something casual. That way, its a little less pressure on you and the girl and you can relax more.