The bus service is provided by Arriva Transport and the main bus station is Maastricht Central. All buses stop there, as well as the international buses to Belgium (Hasselt) and Germany (Aachen). The bus station is divided into two sections: city buses and regional buses.
The city buses will take you everywhere in the city, while the regional buses have destinations like Aachen, Maastricht-Aachen airport, or Valkenburg. The city buses stop at the covered section of the station, the regional and international buses by the bicycle racks. If you’re travelling by city bus make sure you’re on the right side of the platform. The buses at the section closest to the train station go to the outskirts, the buses on the other side head towards the city center. (There are currently constructions underway at the train station. Therefore the covered section is temporarily out of use. Make sure to check the signs at the bus stops for the number of the line you need to take!)
If you need more information on the routes of the different bus lines and you want to see the network map of Maastricht and surroundings, you can download all the Arriva network maps of Limburg. Alternatively, you can visit the Arriva information desk and ask for direct advice. You can find the info desk in the great hall of the Maastricht Station.
Although trains normally represent a faster and cheaper alternative to regional buses, the cheapest and fastest option to get to Aachen is the regional bus number Qliner 350. For €6 you can buy a day pass which counts as a one way ticket to Aachen. If you need to get back to Maastricht, buy a return ticket for €8,50 instead. This site provides the most accurate information on prices and planning your journey.