Registration municipal office
You are legally required to register your place of resident in Berlin. You can do this in every municipal office of every district, hence in entire Berlin regardless in which district you live. You can go there directly without having an appointment for registering. However, this implies long waiting times often. Another possibility is making an appointment beforehand, this is possible by means of internet. If you do this you´ll not have any waiting time.
You have to take the completed form, your identity card and a completed and signed form called "Wohnungsgeberbescheinigung" of your landlord or his representatives with you. If you want to register you and your family you have to take your marriage certificate and the birth certificates of your children with you. If you want to register someone moving in the flat together with you, you need a letter of attorney and the identity card of him.
It is advisable to be there 10 minutes in advance as you may need some time to find the respective office. When registering at the municipal office, you have to register for your personal identification number and the electronic income tax card ELStAM, as well.