Coming to Berlin
You can reach Berlin by train and by air.
Traveling by air
Schönefeld is connected to the central stations in Berlin (Stations: Alexanderplatz, Friedrichstraße, Hauptbahnhof, and Zoologischer Garten) by regional trains (Lines RB14 and RE7), the trip takes about half an hour, and by the S-Bahn (Line S9).
From Tegel the connection to the central stations of Berlin is by buses: TXL will bring you to Ernst-Reuter-Platz (the university is here), to Hauptbahnhof or to Alexanderplatz, and 109 and X9 go to the station Zoologischer Garten). TXL and X9 are express buses, i.e. they are faster because they have less stops than normal buses.
Please note that the links above just indicate the routes but as their schedule can change we highly recommend to check for the current timetables after your arrival.
Berlin has a well developed net of public transport. The most reliable are probably the underground trains (U-Bahn) while the fastest is the S-Bahn. Buses sometimes have delays depending on the traffic conditions, but most of the time the schedule is not violated a lot.
Berlin has 3 areas (zones A, B and C) with different prices. See this map for an overview of the areas. You will probably need only combined tickets for zones A and B (2,80 euros). Note, however, that Schönefeld airport is in Zone C, so to travel between Berlin and Schönefeld airport one needs a combined ticket for zones A, B and C (3,40 euros).
Types of tickets
There are different types of tickets. A single ticket allows to go in one direction for up to 2 hours by using buses, U-Bahn trains, S-Bahn trains, trams, and (usually red) express trains (within the corresponding zone; don't take the white intercity trains for moving within Berlin). One can change means of transportation an arbitrary amount of times during the two-hour period. Baggage transport is free.
It is a little cheaper to buy 4 single tickets at once (4-Fahrten-Karte, 9.00 euros for Zone AB, 13.20 for ABC), but don't forget to stamp your ticket. The yellow stamping machines are in buses (enter at the front door where the driver is), at the entrances to the underground or at the train platforms. There are also cheaper short-trip tickets (you may need to change the language to English). A day ticket costs 7 euros (Zone AB), a 7-days card costs 31 euros (here you can take one person with you for free from 8pm to 3am).
The Berlin traffic company BVG has an app, which can be used both to get information about connections and to buy tickets. However, we recommend to buy tickets via ticket machines at U-Bahn (yellow) or S-Bahn (red) stations or in buses (from the driver)/trams. To check for connections online you can also use more light-weight apps. Popular apps are, for example, Öffi (seems to be currently the best rated one) and DB (the app of Deutsche Bahn). Google Maps is also able to show connections in Berlin, which are often different from those shown in the other apps.
Taxis are somewhat expensive and sometimes not much faster than the public transport due to traffic jams. A taxi can be ordered by a phone call (also in English), e.g., (+49-30) 202020 or by an app. The cost is determined by the distance and is more or less fixed. For example, a trip from Tegel Airport to the Main Train Station (Hauptbahnhof), which is about 8km away, should cost around 20 euros.