I'm no lothario, but there is one universal constant I have seen, that every girl I know finds attractive: Confidence.
Not the brash, chest-thumping bravado that your average loudmouth tool exhibits, but just being able to look at yourself and say, "This is me. It's who I am. Sure, it might not be perfect, but who is?" If you are comfortable in your own skin, and self-assured without being cocky, you will project a sense of calm assertiveness that a lot of women (not all, but a lot) will tune into and at least find appealing - enough to stick around for you to strike up a conversation anyway and wow them with your Star Wars knowledge/Nunchucks technique/freestyle disco dancing prowess.
It's not a magic bullet, but it opens up the possibility that you might be "Boyfriend material" rather than the rather awkward 'Eunuch' figure you are cutting at the moment, if you don't mind me saying.
Confident nice guys are a rare breed, and a good catch, as many guys mistake 'Nice' for 'Spineless.' A confident nice guy has the moral courage to do nice things for others without living for others or allowing themselves to be exploited. And they're not martyrs either. Learn to loosen up and go a bit crazy once in a while!
And how do you become confident? Simple. Act confident. Tell the world that you are a confident man with your body language, voice and actions. It's not easy, but if you keep it up, eventually you will find yourself being confident without needing to act.
Lesson over! For homework, read Rudyard Kipling's poem, "If" for a good primer on examples of confident and nice behaviour.
Cheers!