This is by far the easiest thing you could do to start making yourself more appealing to the lady-types. In many scenarios, women will seem completely uninterested in men in general. This usually comes from them being burned one too many times (by fault of their own poor choices of men to date). They'll constantly say things like, "I'm through with men! They're all such pigs! All they care about is my body!"
But what happens when a musclebound male walks up to them and strikes up a conversation? They go silly! At that moment, all they care about IS HIS BODY. I've seen this happen to the prudest of prudes. Biceps are to women what boobs are to men. Girls act like and say they don't care about physical appearance, but this is just a lie they tell to try to protect your fragile ego, you girly-man.
So seriously, hit the gym. If you're in high school or college, you probably could access their for free. Search the interwebs for good workout routines, and find the one that's right for you. Once you start, you'll look better and feel healthier, and that will give you CONFIDENCE. (Oh snap, it's Law 3.)
Also, always take a bro for moral support. If you go to the gym by yourself, you might become addicted. You'll start slipping into an obsession of constantly working out just to make yourself feel better. And that's masturbation. "Self-improvement" is an oxymoron; we can only grow as individuals through interacting with people who care about us.
Ugh... I need to end this more sarcastically than that...