Everything develops by slow iteration. You'll write something, you'll like it, so you'll do more like it in the future. You'll write something, you won't like it, so you'll do less of it in the future. The more you write, the more you will start to sound like yourself and not like someone else you have been listening to, or like a million disparate ideas competing with each other. There's no trick to it. Just keep composing and be patient with yourself.