Use the strong active versus weak passive voice

From Hamilton College's Seven Deadly Sins of Bad Writing:

The First Deadly Sin: Passive Voice

In most instances, put the verb in the active voice rather than in the passive voice.

Passive voice produces a sentence in which the subject receives an action. In contrast, active voice produces a sentence in which the subject performs an action.

Passive voice often produces unclear, wordy sentences, whereas active voice produces generally clearer, more concise sentences.

To change a sentence from passive to active voice, determine who or what performs the action, and use that person or thing as the subject of the sentence.

Examples:
Passive voice: On April 19, 1775, arms were seized at Concord, precipitating the American Revolution.
Active voice:On April 19, 1775, British soldiers seized arms at Concord, precipitating the American Revolution.

Other examples of passive voice:

1. The process of modernization in any society is seen as a positive change.

2. The Count is presented as an honest, likeable character.

3. Thomas Jefferson's support of the new Constitution was documented in a letter to James Madison.

Overuse of to be (a related problem)

Use of forms of to be (is, are, was, were) leads to wordiness. Use an action verb in place of a form of to be.
Example: It is the combination of these two elements that makes the argument weak.

Revision: The combination of these two elements weakens the argument.