How to write effective sentences?
Rule 1. Use concrete rather than vague language.
Vague: The weather was of an extreme nature on the West Coast.
This sentence raises frustrating questions: When did this extreme weather occur? What does "of an extreme nature" mean? Where on the West Coast did this take place?
Concrete: California had unusually cold weather last week.
Rule 2. Use active voice whenever possible. Active voice means the subject is performing the verb. Passive voice means the subject receives the action.
Active: Barry hit the ball.
Passive: The ball was hit.
Notice that the party responsible for the action—in the previous example, whoever hit the ball—may not even appear when using passive voice. So passive voice is a useful option when the responsible party is not known.
Example: My watch was stolen.
Rule 3. Avoid overusing there is, there are, it is, it was, etc.
Example: There is a case of meningitis that was reported in the newspaper.
Revision: A case of meningitis was reported in the newspaper.
Even better: The newspaper reported a case of meningitis. (Active voice)
Example: It is important to signal before making a left turn.
Signaling before making a left turn is important.
Signaling before a left turn is important.
You should signal before making a left turn.
Example: There are some revisions that must be made.
Revision: Some revisions must be made. (Passive voice)
Even better: Please make some revisions. (Active voice)
Rule 4. To avoid confusion (and pompousness), don't use two negatives to make a positive without good reason.
Unnecessary: He is not unwilling to help.
Better: He is willing to help.
Sometimes a not un- construction may be desirable, perhaps even necessary:
Example: The book is uneven but not uninteresting.
However, the novelist-essayist George Orwell warned of its abuse with this deliberately silly sentence: "A not unblack dog was chasing a not unsmall rabbit across a not ungreen field."
Rule 5. Use consistent grammatical form when offering several ideas. This is called parallel construction.
Correct: I admire people who are honest, reliable, and sincere.
Note that are applies to and makes sense with each of the three adjectives at the end.
Incorrect: I admire people who are honest, reliable, and have sincerity.
In this version, are does not make sense with have sincerity, and have sincerity doesn't belong with the two adjectives honest and reliable.
Correct: You should check your spelling, grammar, and punctuation.
Note that check your applies to and makes sense with each of the three nouns at the end.
Incorrect: You should check your spelling, grammar, and punctuate properly.
Here, check your does not make sense with punctuate properly, and punctuate properlydoesn't belong with the two nouns spelling and grammar. The result is a jarringly inept sentence.
Rule 6. Word order can make or ruin a sentence. If you start a sentence with an incomplete phrase or clause, such as While crossing the street or Forgotten by history, it must be followed closely by the person or thing it describes. Furthermore, that person or thing is always the main subject of the sentence. Breaking this rule results in the dreaded, all-too-common dangling modifier, or dangler.
Dangler: Forgotten by history, his autograph was worthless.
The problem: his autograph shouldn't come right after history, because he was forgotten, not his autograph.
Correct: He was forgotten by history, and his autograph was worthless.
Dangler: Born in Chicago, my first book was about the 1871 fire.
The problem: the sentence wants to say I was born in Chicago, but to a careful reader, it says that my first book was born there.
Correct: I was born in Chicago, and my first book was about the 1871 fire.
Adding -ing to a verb (as in crossing in the example that follows) results in a versatile word called a participle, which can be a noun, adjective, or adverb. Rule 6 applies to all sentences with a participle in the beginning. Participles require placing the actor immediately after the opening phrase or clause.
Dangler: While crossing the street, the bus hit her. (Wrong: the bus was not crossing.)
While crossing the street, she was hit by a bus.
She was hit by a bus while crossing the street.
Rule 7. Place descriptive words and phrases as close as is practical to the words they modify.
Ill-advised: I have a cake that Mollie baked in my lunch bag.
Cake is too far from lunch bag, making the sentence ambiguous and silly.
Better: In my lunch bag is a cake that Mollie baked.
Rule 8. A sentence fragment is usually an oversight, or a bad idea. It occurs when you have only a phrase or dependent clause but are missing an independent clause.
Sentence fragment: After the show ended.
Full sentence: After the show ended, we had coffee.
These rules are taken from http://www.grammarbook.com/grammar/effWrite.asp