Writers try to avoid the passive voice when possible because the passive voice often leads to wordier and less powerful sentences. Instead, writers prefer the active voice because the subject of the sentence is actually doing the action (thus making the sentence more commanding and confident).
Remember, you want to be “active” not “passive” in your writing.
Passive Voice: The midterm exams were graded by the instructor.
These steps help spot a passive sentence and revise it into the active voice:
Side Note: Imagine that you are the director of your sentence, and you have paid your star (a.k.a. the subject of your sentence) a lot of money to act in your sentence. You want them to perform for you.
Active Voice: The instructor graded the midterm exams.
Side Note: The use of “to be” verbs (is, are, were, etc.) is a big tip off that a sentence may be passive (though not always because you can’t completely avoid using them).