It's not an original answer, but it's the most important: read, read, read, and write, write, write. Take advantage of online sites like Wattpad and Readwave to practise your writing and get feedback on your work. Write a blog - even if no one apart from your mum reads it, this will help you find your voice and style and give you lots of practice. And as an editor, I can't emphasise enough how important it is to edit your work time and time again, before pressing that 'publish' button. Many aspiring writers are so keen to share their work that the moment they've finished a story, they publish it. DON'T! Leave it a while - weeks, even - then come back to it. Rewrite, edit. Then do the same again. Check for clarity and consistency, as well as the obvious things like spelling mistakes and typos. The end result – a polished, professional-looking story - will send the message that you are taking your writing seriously.