The easiest and fastest way is to be born with musical talent. Even then, it takes hours of practice everyday. If you don't have musical talent, guess what, you're gonna have to work twice as hard. That's just the way life is. I've been playing piano since I was five. At least an hour a day (which is practically nothing). Piano was my after school activity, it was my sport, it was my video game. It kinda sucked growing up, but now it's paying dividends.
It's also important to know that learning piano definitely gives you a more solid understanding of theory, but it won't do much if you don't have a good ear... meaning, if you can't use your technique to express your ideas, then it's useless. There are millions of pianists, but very few can compose a decent song.