Travel by Air
Stuttgart Echterdingen is the closest airport. From there, the easiest way into Tübingen is the 828 Sprinter bus, which runs hourly and takes approx. 48 minutes to about an hour. For bus schedules, go to http://www.naldo.de. At the bottom left of the page under Mini-Fahrpläne, type in 828 and choose the one with the RBS company.
Alternatively, take the train to Herrenberg, and then the S-Bahn train from there to the airport.
If coming from Frankfurt, it takes about 2 to 2.5 hours with at least a change in Stuttgart and sometimes in Mannheim as well. See Bahn.de and click on the ‘international’ tab for English pages.
Travel by Train
The train from Stuttgart takes about 45min by IRE train or around 1hr by normal train. If you arrive at the main station of Tübingen, don’t let the ugly and uninviting surroundings of the train station put you off. Just leave the station behind and keep going (north) and after 10min. walking you’ll be right in the old town center.
Travel by Car
Finding a spot to park you car can be quite difficult, especially close to the center of the city. Almost every street there may only be used by residents at night, and during the day there are parking meters. Be sure to check the signs how long you are allowed to park there, and if you are not sure, look for another spot. Ticket officers are very quick in Tübingen. If you need to park your car near downtown, you can use parking garages (list of garages in Tübingen), but be advised, they are not cheap.
However, it is best to park your car as soon as possible and then explore the city on foot, bus or bicycle.