Register your address (Anmeldung)
By law you must register your address within 14 days of moving in. The Anmeldung certificate (Meldebescheinigung) unlocks almost everything else: tax ID, bank account, residence permit.
Official source1Book a Bürgeramt appointment
Book online at service.berlin.de — any Bürgeramt in Berlin works, not just your district. Slots are released daily in the morning; check repeatedly or use the all-locations search. The appointment itself is free.
Passport or ID
Official source2Get the landlord confirmation
Your landlord (or main tenant if you sublet) must sign the Wohnungsgeberbestätigung — a one-page form confirming you moved in. Your rental contract is NOT enough.
Wohnungsgeberbestätigung (signed)
Official source3Attend and get your Meldebescheinigung
Bring your passport, the signed Wohnungsgeberbestätigung and the filled Anmeldung form (also available in English). You get the Meldebescheinigung on the spot — keep it safe, everyone asks for it.
Passport · Wohnungsgeberbestätigung · Anmeldung form
Official source
Procedures vary by city and office and can change. This is general information, not legal advice — always check the official source.