Same as every other writer's advice - read read read and write write write. The more you read, the more you internalise the rules of story. You need to get to the point where you instinctively understand what works and what doesn't. And the more you write, the closer you get to finding your own unique voice. Other advice? Cultivate both self confidence and humility. You'll need the self confidence to keep going through all the inevitable setbacks. And you'll need the humility so that you'll seek out good, professional feedback - and LISTEN to it. Writing is about learning, and that never stops.