Berlin has an extensive network of railways which can be fairly confusing for a first time visitor. The national rail service is Deutsche Bahn and it has four train categories. The Regional (RBP), the Regional Express (RE), the Interregional Express (IRE) and the Intercity Express (ICE). The Express lines have trains that do not stop at every station. Tickets can be bought online or at a station, but can be expensive. There are several special offers that can make your travel a lot cheaper so look out for them in newspapers, TV and online. The English language paper ‘Exberliner’ has useful information and news.
Berlin’s S-Bahn and U-Bahn are the underground and above ground metro systems. Information and timetables can be found on the Berlin Transport Authority website (http://www.bvg.de/index.php/en/index.html) or at any station. Look for the blue ‘U’ signs or green ‘S’ signs to find stations. Alternatively, you can call the customer service line of the BVG: 19449. The largest and most popular stations (where you can also buy tickets and expect to be helped) are The Zoological Gardens (Zoologischer Garten), the Lehrter Main Station (Lehrter Hauptbahnhof), Friedrichsstrasse, Alexanderplatz, and Ostbahnhof.
The main station has only been built recently and is a spectacular feat of engineering. Even if you are not expecting to travel by train, visit this station just for the view.
For the purposes of public transport, Berlin is separated into zones A, B and C. Unless you are expecting to do some wide exploring, A zone AB ticket will be practical and reasonable. Zone ABC tickets cost slightly more. The bus, tram, S- and U-Bahn tickets are combined and their price depends on how far you wish to go.
A very handy ticket to initially obtain is the ‘Berlin Welcome ticket’. It can be purchased from the airport station and anywhere that sells transport tickets. Read the information first to find out if it allows travel to where you want to go. Another useful thing to remember is that tickets need to be validated/time stamped on the first trip. This is done by inserting the ticket into a yellow or white machine before catching your train, bus or tram.