Berlin has two airports.

Tegel (TXL), currently the main airport, is 7km northwest of the city centre. Behind the airport information desk in the main hall are the BVG public transport ticket office and the luggage office.

From airport:

By bus
Buses 109 and X9 (the express version) run via Luisenplatz and the urfürstendamm to Zoologischer Garten (also known as Zoo Station, Bahnof Zoo or just Zoo) in Western Berlin. Tickets cost €2.10 (and can also be used on U-Bahn and S-Bahn services). Buses run every five to 15 minutes, and take 30-40 minutes to reach Zoo. At Zoo there are rail and tourist information offices, and you can connect to anywhere in the city (same tickets are valid).
You can take bus 109 to Jacob-Kaiser-Platz U-Bahn (U7), or bus 128 to Kurt-Schumacher-Platz U-Bahn (U6), and proceed on the underground from there. One ticket can be used for the combined journey (€2.10).

Jet ExpressBus
The JetExpressBusTXL is the direct link to Berlin Hauptbahnhof and Mitte. It runs from Tegel to Alexanderplatz with useful stops at Beusselstrasse S-Bahn (connects with the Ringbahn), Berlin Hauptbahnhof (regional and inter-city train services as well as the S-Bahn), Unter den Linden S-Bahn (north and south trains on the S1 and S2 lines). It costs €2.10, runs every 10 or 20 minutes between 4.30am-12.30am (5.30am-12.30am at weekends), and takes 30-40 minutes.
 

- A taxi to anywhere central will cost around €20-€25, and takes 20-30 minutes, depending on traffic and precise destination.

Schönefeld airport (SXF) is 20km southeast of the city centre and is slated to become the main airport in a few years.

From airport:

- Bus X7, every 10 or 20 minutes from 4.30am-8pm runs non-stop from the airport to Rudow U-Bahn (U7), from where you can connect with the underground. When it's not running, bus 171 takes the same route.

- An Airport Express train from here reaches the city centre in 30 minutes; the S-Bahn take about 40 minutes. Take bus X7 to U-Bahn station Rudow for Kreuzberg.

- A taxi to Zoo or Mitte is pricey (€30-€35), and takes around 45 minutes.

By Train

Berlin benefits from a modern, extensive rail service.
Berlin is part of the InterCityExpress (ICE) network, with super-fast trains to Hanover and Frankfurt am Main. ICE trains also go to Hamburg. An expanding web of high-speed trains also serves destinations across Western Europe. Supplements are incurred for travel on ICE, IC and EC trains.

The main railway station is Berlin Hauptbahnhof, Europaplatz, Europe's largest station linking east/west and north/south lines in the city centre. Facilities include tourist information, lounge, bank, restaurant, food halls, café, shops, newsagents, pharmacy, hairdresser and left luggage. Gusundbrunnen station to the north provides rail links to the Baltic. The other major mainline stations are Bahnhof Lichtenberg, and Ostbahnhof, in east Berlin. Some mainline services also stop at Bahnhof Spandau, to the west, and Bahnhof Sudkreuz, in the south.

By Bus
 

Eurolines international coach services cover 500 destinations including Paris, Strasbourg, Vienna and London, and more locally, Frankfurt, Hamburg and Hanover. Berlin Linien Bus also runs these national and international services.
Buses on both international and domestic routes arrive at the Zentraler Omnibusbahnhof (ZOB) Messedamm in Charlottenburg, near the International Congress Centre (ICC). Information and tickets are available from the DTG Ticket Center, Kaiserdamm 30 and at the ZOB Reiseburo.

From Central Bus Station, U-Bahn line U2 runs into the centre.
 

By Road