The booklet Living and Working in Germany from the Max Planck Society has most of the important information regarding visas, health insurance and medical care, finding and renting an apartment and public transportation. It also includes useful checklists for what you need to bring and what you will need to take care of upon arrival. In addition, you can find answers to frequently asked questions on the webpage of the Max Planck Society.
General information on life and customs in Germany can also be found on the websites of campus-germany.de, the Federal Foreign Office, or How to Germany. Also the Alexander von Humboldt Foundation gives some useful hints for your stay in Germany.