My advice

FWIW, my advice is simple....

1. Write everyday. Doesn't matter what it is, just write. You'll get better if you just practice
2. Use your tools. Don't hesitate to look up a definition. New words are new tools
3. Get feedback from a wide range of sources and take note
4. In fact take notes all the time - carry a pen and paper or a PDA, something to jot down ideas
   
5. Write about what you know, or what you want to know
6. Research widely. Get to know your sources and your topic
7. Get out and about, see things, do things and write about them... whenever you can!