William Zinsser wrote the all-time popular book, On Writing Well. Here are some choice quotes from the book:

On the writing process:
Writing is hard, even for the pros, the more you do it, the (slightly) easier it gets. Writing is rewriting. Being a writer isn’t about being a certain type of person, it’s about doing the work.

The purposes that writers serve must be their own. What you write is yours and nobody else’s. Take your talent as far as you can and guard it with your life. Only you know how far that is: no editor knows. Writing well means believing in your writing and believing in yourself, taking risks, daring to be different, pushing yourself to excel. You will write only as well as you make you

Never hesitate to imitate another writer. Imitation is part of the creative process for anyone learning an art or craft…. Find the best writers in the fields that interest you and read their work aloud.

Learn to write about place, because “people and places are the twin pillars on which most nonfiction is built”

Don’t ever become the prisoner of a preconceived plan. Writing is no respecter of blueprints.

On style:
Style is sounding like you on the page, not like anyone else. Zinsser writes:

Sell yourself, and your subject will exert its own appeal. Believe in your own identity and your own opinions. Proceed with confidence, generating it by willpower. Writing is an act of ego, and you might as well admit it. Use its energy to keep yourself going.

On words
Read your articles out loud to see how they flow. Don’t use words you wouldn’t use in the course of normal conversation. Avoid jargon and cliches. Less is more. Active v. passive.

On interviews
Write questions out beforehand. Use some form of shorthand to take notes even if you’re recording. Get more material than you think you’ll need. Pay attention to detail. I didn’t realize how much of this I’d absorbed until I read his chapter on interviews then looked at the notes I’d made for that Digital Journalism Camp class on conducting interviews – his influence is obvious.
You will be resented if you inquire about facts you could have learned in advance.
Learn to interview others and weave their quotes into your writing. “Whatever form of nonfiction you write, it will come alive in proportion to the number of ‘quotes’ you can weave into it as you go along”

On leads and endings
If the first line of your story doesn’t grab readers, they’ll never read the second. Hook them with the lead and keep the good stuff coming. Even when you’re writing nonfiction, writing has to be entertaining for people to stick around. Pay attention to how you finish things. Don’t just re-state the lead – circle back to an opening anecdote, close with a bang-up quote, or simply finish telling the story.

On science, technology and other complex subjects:
Make sure you understand how what you’re writing about works or you’ll never be able to explain it to readers. Avoid jargon. Include people to keep things real.
Imagine science writing as an upside-down pyramid. Start at the bottom with the one fact a reader must know before he can learn any more. The second sentence broadens what was stated first, making the pyramid wider, [and so on.]
Relate [unfamiliar facts] to sights [your readers] are familiar with. Reduce the abstract principle to an image they can visualize.

On editors
Good ones can make decent stories better, and decent writers better too. Bad ones drive writers crazy, by changing style, voice, content, organization, and generally treating them “like hired help.”

On the first paragraph:
The most important sentence in any article is the first one. If it doesn’t induce the reader to proceed to the second sentence, your article is dead. And if the second sentence doesn’t induce him to continue to the third sentence, it’s equally dead. Of such a progression of sentences, each tugging the reader forward until he is hooked, a writer constructs that fateful unit, the “lead.”

Tell a story if possible – “look for ways to convey your information in narrative form.

On humor writing:
Humor is the secret weapon of the nonfiction writer. It’s secret because so few writers realize that humor is often their best tool—and sometimes their only tool—for making an important point.
Don’t strain for laughs; humor is built on surprise, and you can surprise the reader only so often.

On endings:
Like the minister’s sermon that builds to a series of perfect conclusions that never conclude, an article that doesn’t stop where it should stop becomes a drag and therefore a failure.
Conclude with a sentence that jolts … with its fitness or unexpectedness.
The perfect ending should take your readers slightly by surprise and yet seem exactly right. They didn’t expect the article to end so soon, or so abruptly, or to say what is said. But they know it when they see it.

On editing:
Most first drafts can be cut by 50 percent without losing any information or losing the author’s voice

On writing non-fiction:
Every successful piece of nonfiction should leave the reader with one provocative thought that he or she didn’t have before. Not two thoughts, or five—just one.”

On writing reviews:
Criticism should be stylish, allusive, disturbing. It should “jog a set of beliefs and force us to reexamine them.”

On writing memoirs:
Summon back the men and women and children who notably crossed your life. What was it that made them memorable—what turn of mind, what crazy habits?

On travel writing:
Be specific and avoid travelese. Travelese is also a style of soft words that under hard examination mean nothing, or mean different things to different people: ‘attractive,’ ‘charming,’ ‘romantic.’

Grammar advice:
That/which: Always use “that” unless it makes your meaning ambiguous. If your sentence needs a comma to achieve its precise meaning, it probably needs “which.”
Don’t be ambiguous – use personal nouns. For instance, “The common reaction is incredulous laughter” could be “Most people just laugh with disbelief.
Don’t start a sentence with ‘however’—it hangs there like a wet dishrag. And don’t end with ‘however’—by that time it has lost its howeverness. Put it as early as you reasonably can…. Its abruptness then becomes a virtue.
Use exclamation points sparingly. Instead, try to “construct your sentence so that the order of the words will put the emphasis where you want it.
There’s not much to be said about the period except that most writers don’t reach it soon enough.
Good writing is lean and confident.
Use a thesaurus to “nudge your memory.”

[From the Great Books Series. Also see The Success Manual  - Encyclopedia of Advice, which contains summaries of 100+ Most useful books.]