Whenever you can, while you're on the bus or waiting for your turn at the dentist or jogging on the spot getting ready for soccer practice, pick up a book and read. It not only expands your mind and imagination, there are studies that prove it sharpens your brain so that you actually become smarter!
Practice, practice, practice!
Like any skill you have, you can only improve with practice. No violinist or dancer or trapeze artist was ever brilliant at their first attempt.
Write about things you care about
If you're excited about what you're writing about, hopefully that excitement will be infectious and your reader will love what you're writing too.
Go on, what are you waiting for?