This piece by Raul Pacheco-Vega hits some very important points.
1. Write every day.
2. Give yourself the best tools to write.
3. Write as you would speak (aka, read it aloud as you write).
4. Have others read to give you feedback.
5. Read a lot, read across disciplines. [I would say read good writers.]
6. Write for your audience.
7. Write without interruptions.
9. Practice your writing by writing a lot.
10. When stuck, write by hand.