The public transport network in Aachen is often overcrowded and delayed, but the buses run at a very high frequency throughout the day as well as and a more limited nightly and weekend service. As a student, you will receive a student semester ticket for public transport throughout the entire state North-Rhine Westphalia (i.e. regional trains, buses, etc., Note: this excludes IC, ICE, and Thalys trains). This is paid by your semester fee.
There is a very useful app, called DB-Navigator, available for Android and iOS which calculates the fastest connection between any two locations in Germany. You can type in a street and house number and the app will find the closest station. A similar program is used on the website www.bahn.de. Sometimes the buses have so much delay, that you miss the following connection.
The local bus company for Aachen is called ASEAG and it is member of the transport association AVV. They also have an app, ASEAG mobil, which displays arrival and departures in realtime. You can print out all bus schedules for Aachen on http://avv.de/de/linienfahrplaene or access a trip planner at http://aseag.de
The bus stations close to main campus are called “Technische Hochschule”, “Driescher Gässchen”, “Ponttor” and “Audimax”.
Buses to the Melaten campus run frequently as well.