The public transportation system in Berlin is very good. Berlin has now 3.5 million citizens. It is a big city. But you can reach nearly every point with the public transportation. Take advantage of S-Bahn, U-Bahn (Underground / Subway) and Buses. This is the official Homepage for the Berlin public transportation: BVG. And here is another page: http://berlin-germany.ca/transportation/transit.html
A regular ticket cost 2.40 EUR. A regular short trip ticket only 1.40 EUR. Or you just buy a monthly flatrate for 77 EUR.
This is the Main Rail Station.
In this direction you can drive to “Zoologischer Garten” and Charlottenburg.
And the other direction brings you to “Alexander Platz”, via “Friedrichsstrasse” and “Hackscher Markt”.
And this here is Alexanderplatz.
Alexanderplatz is very famous because of the TV Tower. This is a big Hub for the public transportation.
During the rush hour it is very crowded. And this is the U-Bahn station at Alexanderplatz.
Usually not as crowded as the S-Bahn station. In the morning and in the late afternoon the public transportation is usually full. And you have to stand.
But still better than sitting in the car. And this is Hackscher Markt.
All announcements are in German and in English. With the public transportation you can reach every neighbourhood in Berlin. But in most cases you have to switch a least 1 time between U-Bahn, S-Bahn and Bus.
If you have an iPhone I recommend you the “Fahrinfo” App. It is the official Berlin public transportation App. I don’t like it very much, but it works … usually!