How to integrate Gallery2 into Joomla?

Everyone who worked for a while with Joomla! and Gallery2 knows that there some difficulties whenever you try to combine these too. It is possible, to say this first, but there are some files you need and some things you better know. The normal way to get it run ist to start the usual never ending tour through all the kown forums. It usually takes time.  This is why I have tried to collect the necessary information on the subject. You also find the files you need within the download section of this page. If it happened that there is any new files on the subject and I 1. not  been run over by a public bus, or 2. have been run away to an unknown island or 3. try to be a shepard on a Swiss alp, I will upload the new files right away. But we better start with the important stuff...