Construct the sentence so that the actor performs the action. A constitutional amendment to ensure a balanced budget was proposed by both conservatives and liberals. That should be the subject. If the subject performs the action, the verb is in the active voice. If the subject is acted upon, the verb is in the passive voice.
Active voice is dynamic.
Passive voice is static. This is particularly important in headlines. Your reporter calls with the information below the story from his police beat. Combine the two sets of information into one story, no more than six paragraphs. After apparently playing possum, a state prisoner disappeared early today from the work release center here.