Berlin is massive and well spaced out so public transportation is a necessary daily activity. The city is made up of 3 zones in terms of transport - The inner city which is circled by the S-Bahn ring (urban rail-line) from this S-Bahn circle to the city boundary and the Greater Berlin area which includes areas such as Potsdam and the airport.

Don't risk journeying without a ticket as inspectors issuing €40 fines are fairly commonplace. Short-trip tickets are €1.60 (up to 3 metro stops), single tickets are €2.70 for longer journeys but if you're heading out and about, as you should be, the best option is a day ticket for €6.90 allowing for unlimited travel in a 24 hour period.