Avoid The Passive Voice

Active: Allison (subject) went (action) to the store to buy a cake (object).

Passive: The cake (subject) was bought (action) by Allison (object).

It's easy to spot the passive voice by looking for the verb form "to be" accompanied by another verb in the past tense (like "was bought" above). Sometimes the passive voice is necessary because the subject of the action just isn't known. When it's not necessary, the passive voice is not good usage.