Read also (below): A list of popular misconceptions about the defense registration
1) Before registration
2) Between registration and the PhD defence
3) After the PhD defence
Some information about the PhD defence, with forms in English, can be found at: http://www.fundamental-physics.uni-hd.de/index.php?m=5&s=5
This web page has an English version of the final exam application form: http://www.fundamental-physics.uni-hd.de/content/en/zubehoer/anhaenge/finalexamination/3_Gesamtfakultaet_Zulassung.pdf
As you know, it's the student's responsibility to find the 4 examiners and to get an agreement on a date of the PhD defence. The examiners have to be from three different fields of physics (see the list of fields in the second page of the "Registration form"). There is a list of potential examiners (as of December 2013). You may try to get the latest version via the directory listing.
Remember also that there is a defined schedule for registering, submitting your thesis and conducting your PhD defence. For instance, for a PhD defence planned for 19th November:
The current schedule can be found at: http://www.fundamental-physics.uni-hd.de/index.php?m=6&s=7
At the end of this document it states that "Additional dates for examinations within term time can be organized upon request", so you should be able to changes dates, but some students have reported having had problems with this.
Ms. Harbers of the Dean's Office has confirmed in August 2012 that examination dates can also be set on other weekdays. If all Wednesdays are taken, Thursdays and Fridays are also recommendable as they won't prepone any of your deadlines. In terms of dates, finding one where all the examiners are available may be the bigger hurdle.
As of August 2012, all astronomy candidates (including those not registered via HGSFP) are administered by the HGSFP office. It seems you have to register for the defense there, not at the Dean's Office.
Submit your thesis and all the other documents to the administration. The complete list of documents to give to the administration is given here, at "(4) List of all documents ..." : http://www.fundamental-physics.uni-hd.de/content/en/zubehoer/anhaenge/finalexamination/1_Doctoral_Exam_rules_and_regulations.pdf
A popular place for binding your thesis is Baier Digitaldruck. They have outlets in Mönchhofstraße (phone 4577-11) and in Neuenheimer Feld. You can bring them printouts and the binding then costs 5.40 € (up to 150 sheets, i.e. 300 pages if printed duplex). They give discounts if you print more than 20 pieces. You can reclaim the money from the Patzer found. Binding takes about 1 day. You will need to submit 10 copies to the faculty.
You can also send emails to the examiners to remind them (1) to send their report and (2) the date, time and location of you PhD examination.
When you recover from your PhD defense, you have to do two things.
First, you have to bring your thesis to the University library. To do this, you have to bring 4 copies of the 10 copies you first gave to the Dean's office before your PhD defence. Make sure that one of the 4 has the special stamp from the Dean's office. You also have to submit a PDF file of your thesis here :
http://archiv.ub.uni-heidelberg.de/volltextserver/doku/heidok_publ.php?thema=ext_howto&la=en
Upload your thesis and print the form (that requires your signature) and give this to the University library. Then, the person in charge at the library can sign the paper (see the link below) that you have published your thesis at the University library.
Second, you have to do an "unregistration" at Heidelberg University (or "exmatriculate"). I'm aware that there are (maybe) people sho didn't do this and seem to have no problems at all. However, if the question is << Do we have to do an "unregistration"? >> then the answer seems to be yes, based on the rules.
The following form (only available in German) can be used : http://www.uni-heidelberg.de/imperia/md/content/studium/download/allgemein/exmatrikulation.pdf
First, go to the University library and get the stamp for the exmatriculation document in the "Ausleihe" in the back left corner of the ground floor. This is done in order to prove that you don't have any books checked out from the library. Afterwards, you need to go to the "Studentensekretariat" and go to the office that has your last name on it, which is different depending on whether you are from Germany or not. You give them your form with the stamp from the library that prove that you don't have any books checked out from the library. You finally get a document that prove that you have unregistered from Heidelberg University.
If you have any new information or comments, please add them.
Good luck for your thesis defence (and thesis writing for those in that step).