Read the best authors for the intended style, be it story-writing, critical analysis or business communication. It all depends on the style of writing you would like to master. It's theor techniques that you want to emulate and make your own.
Write to evoke an emotion. There must be a purpose to your writing. If to inform, guide the reader to an ah-ha moment. Your writing will be memorable if the reader feels something.
Cut fluff. Every word must have a purpose. Less is more.
Good writing is about refining your own voice. Write as you speak, speak as you write, and both will improve.
Ultimately, have fun with it. Experiment with different styles. Writing is an art, it requires creativity. This must be cultivated and grown. In time, over many poorly crafted drafts, a unique voice, all your own, will emerge.
Best of luck!