"Passive" does not refer to "past" tense. It refers to active vs. passive subjects and verbs. In literary analysis, always write the subject with an active (rather than passive) verb:

Example (passive):  The character is described as foolish.

Revision (active):  Dorine describes Tartuffe as foolish.

When you revise, search for and revise "be" verbs (in this case "is") as a way to avoid passive voice - the actual active verb will always follow the "be" verb (in this case "describe"). Notice that revising the passive voice demands a more specific subject (in this case, Dorine, a character in Moliere's Tartuffe). Active voice generates more specific analysis and content.

In addition to your New Century Handbook guidelines, these web sites may help you understand and correct passive voice.

Web Sites / Aides:

Plain Language Site

Princeton Writing Program   (requires Adobe Acrobat)