Tell your readers something new. That's why they pay for the content. Keep them in mind, always. Know who they are and write to be read by them. If you think you can tell your readers to go to hell, you'll be the first to get there. And so will the publication you're writing for.
Write plain, simple English. Simple words are the most powerful. Don't say: "Alternative procedures for the realization of these objectives will have to be drawn up." Say: "We need new ways to do this." Remember, easy reading is damned hard writing. And tell yourself you need not impress with fancy writing. If you can, make your words sing. If you can't, at least make them clear.
Never use a long word when a short one will do. Use active verbs. Do not turn verbs into ugly nouns. Strike out "very" always. When reporting the news, strike out most adjectives. You can do without them if the verb is strong. Besides, a good story does not need decoration.
Learn to edit your own copy. The easy part about writing is you don't have to get it right the first time – unlike, say, in brain surgery. Even the best writers say the best writing is rewriting. Until you can spot the flaws in your writings, you aren't a writer.
Be obsessed with accuracy. It is paramount. If you don't treat facts as sacred, you should be a fiction writer. Don't make stupid mistakes like getting someone's name wrong. Readers will say, "If you can’t get small things right, how can I trust you with the important things?" So check and re-check your facts. If in doubt, leave them out. Never report rumors. And never ever make up quotes or doctor them to make them sexier.
Read every day – three, four books at a time and all the magazines you can lay your hands on.
Feed your mind as you feed your body, every day. A prize-fighter cannot fight on the beef steak he ate 10 years ago. Writers cannot do good work on the thinking of 10 years ago. Keep your mind open to new ideas and think.
Learn your craft. As you learn, some grinding of the teeth is allowed, but not too much. No one puts a gun to your head and orders you to be a writer. You become one out of your own free will (hopefully).