Try the Berliner Verkehrsbetriebe (BVG). They are not striking.
You can install the BVG Fahrinfo application and give in precise details.
Depending from where you start, find an underground connection that crosses the U7 (most North/South lines cross it)
- U9 (Bahnhof Zoo): U7: Berliner Straße
- U6 (Bahnhof Friedrichstraße): U7: Mehringdamm
- U8 (Alexanderplatz): U7: Hermannplatz
Below is a screenshot for Tuesday, 10:00.
Take the underground (U7) to Rudow (on the map where the blue line ends) and then the X71 (every 10 minutes) to the Airport (Terminal 1-2).
An ABC ticket (€4.00) is required
- or an AB ticket (€3.20) plus a connection-card (Anschlussfahrausweis) for €2.00 (which you can stamp when the journey starts)
- most of the Tourist/24h cards are for the AB area
Zone C starts at the city limits, which the X71 will cross. So the connection-card must be stamped at the latest when getting on the X71 Bus.
The BVG app [Fahrinfo] is also very useful because it gives you very current routing based on very up-to-date conditions, even things like real-time train delays.
Why, just yesterday I thought I was being smart by taking an earlier tram on a different route that would get me towards my destination, even though it wasn't indicated by the app.
Turns out a segment of that route is closed for building work and replaced by bus, which is why it wasn't suggested.
And yes, it shows you all services not just BVG services.
This is also true for special events, such as Marathons, which often block north/south bus connections on Saturday/Sundays. Based on the given date/time of arrival you can see if the bus line is effected or not, with alternative routes being suggested to bypass the area of the event.
The services (Bus, Trams, U-Bahn, S-Bahn) can be turned on/off effecting what is shown on the map and used for the suggested route. Pressing the icon can set the destination/starting point.