It’s really useful to have a reference guide to how to use the passive in a large variety of tense constructions. So here you have it. There are passive and active equivalents and then at the back there is a comparison with English and German.
(Adapted from: http://www.englishpage.com/verbpage/activepassive.html)
Note that there is nothing about when to use it, only the correct form, but as far as I can tell so far, it’s more or less the same in both English and German. Correct me if I’m wrong about that 🙂