Writing gets better by doing, so the simplest way to improve, is to do lots of it. I think it is also important to read a variety of genres and try your hand at different kinds of writing. You never know what you're good at until you try that. If you've just started, don't get hampered by thoughts of getting published. Just let the book that is in you, come out. Whether you think you're brilliant or whether you think you're the pits, on both counts, you're probably wrong. Develop your skill, your character and plot building, then study the market. Don't hesitate to ask questions. Be always ready to learn.