Freiburg is a city built for walking and cycling. The old town is fully pedestrianised, the centre is small enough to cross on foot in fifteen minutes, and almost everywhere you might want to go is within thirty minutes' walk of the Münster.
Trams (Stadtbahn) run from early morning to about midnight on five lines, fanning out from the old town. A single ride costs around three euros; a 24-hour Regio24 ticket is much better value if you plan to use the system more than twice. Tickets are sold at machines on the platforms and must be validated before boarding.
Bicycles are everywhere. Freiburg has a higher cycling share than most European cities and the network of bike paths is excellent. Rentals are available at the train station and at several shops in the centre.
Cars are awkward — much of the old town is closed to traffic and parking is expensive. Drop your car at one of the park-and-ride lots on the outskirts and take the tram in.