the only way you will ever become "alpha" is to go out and seriously live life. it's not in a book, a wardrobe, a few choice words, it's in becoming battle tested, battle hardened, taking serious risks in life, taking chances, doing what you wish to do, failing, picking yourself up and dusting yourself off.
alpha is having lived life to the point where that 5'10 blonde with those long skinny legs dangling her shoe off her toes and twirling her hair isn't that scary anymore. it's just a chick. she either will **** you or she won't either way it's not the end of the world.
you have to live life. there are very few people who actually go and grab life by the nutts and live it to it's fullest extent. push themselves to be better everyday, try new and interesting things, learn new things, try whatever crazy idea they come up with, whatever it is you deem necessary do that ****. the more you come out of your shell the more your uniquness will broadcast itself to the rest of the world without you having to say a thing.
in short, you can't convince a girl you are alpha. it's just something you are.