The passive voice is bad in so many ways: it’s weak, it leaves out important information, and it can be confusing to readers. Just don’t do it!
So how do you identify passive voice in your writing? Go back to basic English: every sentence must have a subject and a verb. Can you find the subject? If not, you’ve got a passive sentence. If you can, but it’s not at the beginning of the sentence (as part of a construction like “was [verbed] by …..”), you’ve got another passive sentence. Let’s look at an example to help us. Take the famous Nazi line:
Mistakes were made.
By whom? Where is the subject? (see the illustration at left). So you might revise to include the subject:
Mistakes were made by other officers.
Better, but still passive. Try rewriting it in basic “subject-verb-object” structure:
Other officers made mistakes.
Can you see how much clearer, more direct, more powerful, that sentence is? So when you want your writing to be clear, direct, and powerful (which should be most of the time), avoid the passive voice!