Arriving in Germany: Public Transport
If you arrive in Germany at the Cologne/Bonn airport, you can get to the main bus and train station in Bonn by bus. The bus departs from the first basement of the Cologne/Bonn airport. It is bus number SB60 with destination "Bonn Hauptbahnhof" (Bonn Main Train station). Tickets can be bought from the bus driver or at ticket machines for local transport (indicated by "VRS" = Verkehrsverbund Rhein-Sieg, the local provider of public transport).
Be careful with taking taxis, as they are very expensive.
If you arrive at some other airport, you can get to Bonn by the regular train (called the Regional Bahn, RB) or the (more expensive) fast train (IC or ICE; Inter-City Express) from the airport you arrive at. Please always buy your ticket before getting on the train. If you have any questions, ask at the information desk at the airport.
Transportation between Campuses
The University has a campus in Hennef (Department of Social Security), a campus in Rheinbach, home of the Department of Natural Sciences and the Department of Business Administration, whereas the main campus is located in Sankt Augustin with all other departments and the administration. Bonn is situated more or less between both cities, and transport between both is easily done with bus and/or train.
To get to the campus in Rheinbach, you take the train (S 5) going to "Bad Münstereifel", "Euskirchen" or simply "Rheinbach," as indicated on the top of the front of the train, departing from platform 5. In fact, it is the only train that departs from this platform so chances to catch the wrong train are nearly non-existent. From the train you can already see the University buildings.
To get to the main campus in Sankt Augustin from the Bonn main bus and train station, you will need to use the underground number 66, which heads to Siegburg. Get out at the "St. Augustin Zentrum" stop. From there, walk across the footbridge and pass by the shopping mall. Then, follow the posted signs to the Grantham-Allee or simply all the other students who are on their way to campus.