Groningen's bus network is small but efficient, with buses running from around 06:00 to 24:00, and a night bus network. At the bus stop, stick out your hand to be sure it will stop for you. 'Eurokaartje' tickets are most practical for short-term visitors, and can be bought from the driver. Tickets cost €2 for rides within 2 zones (Groningen centre and suburbs, valid for an hour), or €5 for rides on the night buses. A bus day ticket, valid for the provinces of Groningen and Drenthe plus part of Friesland, costs €16.
Longer-term visitors can get much cheaper fares by investing in an OV-chipcard, the payment card for public transport throughout The Netherlands. Using the OV-chipcard, a single bus trip within Groningen costs around €1, the ride to the airport €3,26. Swipe the card against the terminal; every time you get on and off any bus or train, and the fare is automatically deduced. An 'anonymous' card can be bought for €7,50 at train or bus stations, and can be charged at the counter or at loading devices in stations, supermarkets and newsagents. See www.ov-chipkaart.nl for details in English.
The Qbuzz website has local timetables, but the handy www.9292.nl website is in English and covers connections throughout the country.