What are the most common prerequisites demanded by Promotionsausschüssen (German PhD boards)? Reading the German universities' regulations on doctoral programs, one often comes to paragraphs about sanctions that can be demanded by the PhD board (Promotionsausschuss) as perquisites before they admit a candidate.

For example I have seen [updated to reflect the given answers]:


own publication(s) needed
take selected courses/modules offered by the university, which contents are related to the planned topic of thesis
submitting an exposé
letter(s) of recommendation
certificate of good conduct ("Führungszeugnis")
supervisor actually employed at the same university




Are there other common requirements demanded by such boards?
Other requirements (not necessarily prerequisites) may include the attendance of doctoral seminars (i.e. presenting your work one or more times during your PhD and having a committee judge whether or not you can proceed as intended) and the presentation of a certificate of good conduct ("Führungszeugnis"). 

Source: http://www.inf.ovgu.de/inf_media/downloads/forschung/promotion/2013/Promotionsordnung_2012_12_19-p-4194.pdf