[If you want a copy of this text as learning support in Microsoft Word you’ll find it under that hyperlink.]
“Use the active voice.
The active voice is always more direct and vigorous than the passive:
I shall always remember my first visit to Boston.
This is much better than
My first visit to Boston will always be remembered by me.
The latter sentence is less direct, less bold, and less concise. If the writer tries to make it more concise by omitting “by me,”
My first visit to Boston will always be remembered,
it becomes indefinite: is it the writer or some undisclosed person or the world at large that will always remember this visit?
This rule does not, of course, meant that the writer should entirely discard the passive voice, which is frequently convenient and sometimes necessary.
The dramatists of the Restoration are little esteemed today.
Modern readers have little esteem for the dramatists of the restoration.
The first would be the preferred form in a paragraph on the dramatists of the restoration, the second in a paragraph on the tastes of modern readers. The need to make a particular word the subject of the sentence will often, as in these examples, determine which voice is to be used.
The habitual use of the active voice, however, makes for forcible writing. This is true not only in narrative concerned principally with action, but in writing of any kind. Many a tame sentence of description or exposition can be made lively and emphatic by substituting a transitive in the active voice for some such perfunctory expression as there is or could be heard.
There were a great deal of dead leaves lying on the ground.
Dead leaves covered the ground.
At dawn the crowing of a rooster could be heard.
The cock’s crow came with dawn.
The reason that he left college was that his health became impaired.
Failing health compelled him to leave college.
It was not long before she was very sorry that she had said what she had.
She soon repented her words.
Note, in the examples above, that when a sentence is made stronger, it usually becomes shorter. Thus, brevity is the by-product of vigor.”
Excerpted from: Strunk, William Jr., and E.B. White. The Elements of Style, Fourth Edition. New York: Longman, 2000.