The Passive Voice in German

ACTIVE/AKTIV
Ich schreibe den Brief.
I'm writing the letter.


PASSIVE/PASSIV
Der Brief wird von mir geschrieben.
The letter is being written by me.


To form the passive, German uses
werden (to become) + the past participle,





Substitutes for the Passive:

"man": This construction uses the active voice but still manages to avoid identifying the subject:

Man kann den Wagen leicht reparieren.
One can repair the car easily.

Man schleppt den Wagen ab.
One tows the car away


"sich lassen": This construction often implies "können:"
Der Wagen lässt sich leicht reparieren.
The car is easy to repair/can be repaired easily.


reflexive: with some verbs, there is an English equivalent, without the reflexive, but usually not:
Wie schreibt sich dieser Name?
How do you spell this name?
Das versteht sich von selbst.
That goes without saying.

"sein" + "zu": This construction implies "können," "müssen," or "sollen," and sometimes is equivalent to "is/are to" + passive
Der Wagen ist leicht zu reparieren.
The car is easy to repair.


References:
http://www.dartmouth.edu/~german/Grammatik/Passive/Passiv.html
http://german.about.com/library/weekly/aa012901a.htm