From Tegel Airport:

Take the bus X9 or 109 to the Zoologischer Garten stop (about 15-20 minutes). At Zoologischer Garten, change to the subway U9 (orange line) in the direction of Rathaus Steglitz. Take the U9 two stops to Spichernstr. station (About 3 minutes). There, change to the U3 (turquoise line) in the direction of Krumme Lanke. Take the U3 five stops to Thielplatz station (8 stops, about 15 minutes). From Thielplatz it is a 2-minute walk. Esitmated travel time about 40 min. A ticket from Tegel airport will cost 2.40 € and is valid for 2 hours.You will need a Berlin AB ticket which you can purchase at the vending machines next to the bus stop. You should show the ticket to your bus driver, then stamp the ticket in the small ticket validation machine mounted on the pole to your left after boarding the bus.

From Schönefeld Airport:

Take train S9 in the direction of Blankenburg (dark red line) to Adlershof station. Change there to the circle line S46 (brown line) on Track 4 in the direction of Westend.  From Adlershof travel west to Heidelberger Platz (about 20 minutes), change to the subway U3 (turquoise line) in the direction of Krumme Lanke. Take the U3 five stops to Thielplatz (8 minutes). Estimated total travel time: about one hour. A ticket from Schönefeld airport will cost 3.10 € and is valid for 2 hours.You will need a Berlin ABC ticket which you can purchase at the vending machines just in front of the entrance to the platform. Be sure to stamp your ticket in the ticket validation machine mounted on a post just before entering the platform.

From Hauptbahnhof (Central Train Station):

Take any of the trains on Track 16: S5, S3 or S75 in the direction of Westkreuz, at Westkreuz change to Track 12, either the S41(circular line) or S46 to Heidelbergerplatz). There, go downstairs to change to subway U3 (turquoise line) in the direction Krumme Lanke. Take the U3 five stops to Thielplatz (8 minutes). From Thielplatz it is a 2-minute walk to Boltzmannstr. Estimated travel time about 45 min. The ticket from the central train station will cost 2.40 € and is valid for 2 hours.You will need a Berlin AB ticket which you can purchase at the vending machines throughout the station. Be sure to stamp your ticket in the ticket validation machine  mounted on a post before going to the platform.