As a general rule, cast your sentences in the active voice.  In the active voice, the subject of the sentence does the action. In the passive voice, the subject of the sentence is not the agent doing the action. Instead of writing, “The cat was kicked by Joe,” write, ” Joe kicked the cat.”  It means the same thing, but the ability to express an idea in fewer words helps to clarify your meaning and makes the readers’ job much more pleasant.  It doesn’t seem like much when dealing with a simple sentence–three words instead of five–but compounded over the course of an extended essay, this can represent a significant amount of extraneous prose.

Weak verbs: is, are, was,were, have, has, had, am,

Strong verbs: Any of the thousands of action words such as “run,” “study,” “eat,” “remember,” etc.

Examples:

Kenia is an author of novels.  (weak–passive)

(Revision) Kenia writes novels.  (strong verb–active)

Gary is a member of the club. (weak)

(Revision) Gary belongs to the club. (strong)

Yamen was of the opinion that it would rain today.

(Revision)  Yamen believed it would rain day.