Public transport is organized in Berlin through the VBB fare network. This includes all public transport of the BVG, such as buses, metro and tram, as well as the S-Bahn.
Tickets can be purchased online as well as at ticket machines at the subway or S-Bahn stations, or directly on a bus. Please remember to validate your ticket before the ride.
Please note that there are three different fair zones (A, B and C). Most tickets are for fair zones A and B. If you want to get out of the city, you have to buy an extension ticket for zone C.
You can find an overview of all ticket prices here.
Subway: U2 Potsdamer Platz
S-Bahn: S1/S2/S25/S26 Potsdamer Platz
Bus: M48/M85 Kulturforum; M41 Philharmonie Süd; M29/M48/M85 Potsdamer Brücke; 200/M41/M48/M85 Varian-Fry-Str.