Textbooks on how to improve your writing run to hundreds of pages, and they are full of learned opinions presented as truth. The truth is, good writing is an art, like dancing. The truth is, you cannot reduce it to rules although without rules it's hard to do. Good writing is easier to identify after it's written than it is to predict. This is why so many bad teachers are better at judging your writing than at improving it.
So if you want to be a good writer, what are you to do? A few simple things will shift your direction to something good. Here they are, in a list you can explore details of by clicking on "More." Note: I'll be adding more "Mores" until there's one for each item, so you might want to bookmark this page.
1. Have and use good reference books. That means one "grammar handbook"; it hardly matters which one, and one dictionary. If you are serious about writing, you should own a copy of Strunk and White's Elements of Style. Don't think of it as your rule book, but as your membership card in the club of people who take writing seriously. Own it and read it, in sips and nibbles, paying attention.
Regarding dictionaries, if you always write on a computer with an Internet connection, then bookmark m-w.com. That's the online Merriam-Webster dictionary, and it's always there when you need it. You should also own a general dictionary that is less than ten years old and weighs more than two pounds. That's right. It doesn't matter whether your dictionary is Barlett's, Webster's, the Random House, the Oxford, or the American Heritage. What matters is that you keep it handy and use it wisely.
Grammar handbooks are also important references and most of them are more than adequate to the needs of anyone but a purist. Any secondhand edition of the Harbrace Handbook will do you just fine, as will any college handbook by Hans Guth. I love Frederick Crewes' Random House Handbook, but that's simply a personal preference. If a handbook is used in the classroom somewhere, it's probably good enough for casual rule checking. Big used book stores, especially near college campuses, will have old editions, quite cheap.
Other references are useful but not crucial. More...
2. Think about writing when you read. Spend some time each day reading for pleasure, and include in the pleasure thinking about how things are written. Read sentences out loud. If you have trouble understanding something, read it analytically to determine why it isn't clear. Nothing teaches good writing better than reading. If you read unconsciously, without analyzing the writing, you will learn to write better eventually, just as going out dancing every night is fairly likely to lead to better dancing. But if you are in a hurry, then think about the writing itself rather than letting it wash over you. More...
3. Read what you write aloud. As literacy drops across the country, it's safe to assume that many of your readers will "subvocalize" (tech-talk for "read silently") as they read your work. So they are going to hear it when they read it. What does your writing sound like, then?
Have you ever heard yourself on tape or voice mail and thought, "That's not what I sound like!" or at least, "Do I really sound like that?" Face it: You do. And you need to know how you sound when you write. It's not just a clever metaphor, that your writing style is called a "voice." We "listen" as we read. If you don't listen to your own "voice," how will you know what they are hearing? More...
4. Punctuate your pauses. A side benefit of reading aloud is that you will discover how to use punctuation more effectively, regardless of how many rules you've had drilled into you. As you read aloud, any natural pause is a place to consider putting a comma, semi-colon, or period. But which? Well, your sentences should be 10-40 words long, and a sentence shouldn't have more than one semi-colon or a half dozen commas. This is called "rhetorical punctuation," by the way, and much frowned on by teachers. But used with a grasp of punctuation rules, it works.
5. A paragraph should be less than two inches deep. Since we are into blasphemy here, let's handle the "single idea" notion of paragraphing. A paragraph is not a "single idea"; it's a visual element that helps people read. "Kumquat" is a single idea, and so is Othello. Paragraphs are machinery, not ideas. If your paragraphs are more than two inches deep on the page, people will be daunted. And yes, that means to break up your text more frequently as the type gets smaller and the line narrower. Really!
6. Learn to whittle words. No, I don't mean "whistle." We talk about "polishing" text, but whittling is usually needed more than polish. By "whittle," I mean removing words here and there. Any editor will tell you that what people write is likely to be reduced by editing. That's because we don't write efficiently. (And because of a tragic reality of composition teaching that I'll get to later.) A drill to reduce word counts will almost always improve your writing.
A good strategy for trimming is to count the words, then decide you will cut 10%. Got 500 words? Have to cut 50. Then you work through the text, cutting at least one word from each sentence. Snick; whit: That's "whittling." It's not at all like hacking off whole sentences or paragraphs with an axe. Why does it work? Because it forces us to look at each word carefully. It forces us to slow down and pay attention, which is half the writing battle.
7. Set length goals for sentences and meet them. Use your word processor's readability or statistics tools to measure sentence lengths, and choose a maximum (17-20 words is reasonable), then crop and edit to see that no sentence exceeds the limit. That's no sentence. Got a string of verbal pearls you can't part with? If it's too long, then make it two strings.
Select a sentence you are unhappy with, and decide that you will rewrite it so that it's 20% longer or shorter. For example, if the sentence is 23 words long, and you pick 20% longer, you must make it 27 words long. Once you get started, you will probably change a lot more than four words, throwing some out and making substitutions. But stick to the goal: 27 words. This is a great discipline that teaches you to look carefully at the actual writing, rather than muse over the ideas. Hardly anyone has the patience to do it. Patience, on the other hand, is the key to success.
8. Proofread backwards. Spelling is the most trivial element of communication and the one that most readers can spot. Can't spell "guarantee"? There goes your cred, Ph.D. or no. It's a crock. Many famous writers are famously bad spellers. Add to the spelling problem the typing problem (I know there is no such word as 'teh', but I can't write a page without typing it), and you have text zits that your readers will notice and judge you by. How to solve the problem? Well, you can run the spell checker on electronic copy. This is usually a fun exercise, since the computer is given to asking if you meant "sprigs" when you typed "spriing" or "mudslinger" when you typed "Salinger."
Needless to say (well, Ok, not really, or I wouldn't say it), Don't trust the computer's judgment! Its ideas about spelling are often asinine, primarily because it just looks at the word, not the surrounding context. It licks spilling lack this. And never, ever, take at face value the computer's suggestions about grammar. Never. When I run MSWord's grammar checker on a 1,000-word essay, at least 90% of its suggestions are wrong. Just wrong.
9. Write short. Computer grammar checkers are good for one thing: helping you identify long, complicated sentences. This gives you a rough idea of the "readability" of your writing. Readability means how literate must someone be, just to be able to read your sentences. A "readability index" above 12th grade means you are writing for college professors: sad, but true. Long, complicated sentences are a challenge for all readers (even, bless them, college professors). Do you want to challenge readers with your ideas? Great; go for it. But don't challenge them with getting through your sentences. That's like inviting them to dance in sand. When my writing is hard to understand, my ideas are buried in noise. Write simple. Shakespeare did.
10. Team up. Writing is a collaborative activity. Your collaborator may be the reader you never hear from and thus can only imagine, but if he doesn't like what you read, and you wanted him to, that's bad. So bring the reader face-to-face, and listen to her. Always listen. In my professional work, I listen to people telling me how to fix something I've written, figure out why they think it needs fixing, and fix that. Many times, their offered fix is not the solution, but it helps me figure out the problem. If someone says my sentences are too long, I know they need work, or he wouldn't have noticed.
Have someone else read your work and "edit" it. Thank them for their notes and suggestions and offer the same in return. They may not know grammar and proofreading marks, but they can say, "I don't get it," and when they don't get it, that's your problem not theirs. Writing is not sacred. Or rather, it is too sacred to be done alone, carefully expressing your "self" like a blackhead.