Buses and trams operate throughout Potsdam. The most useful line is bus 695, which connects the Hauptbahnhof with the Altstadt and Park Sanssouci. Tickets costs €1.60 and a day pass €3.70.
For bike hire, try CityRad (0177-825 4746; per day €11; 9am-7pm Mon-Fri, to 8pm Sat & Sun mid-Apr–mid-Oct) outside the Bahnhofspassagen at Potsdam Hauptbahnhof (exit Babelsberger Strasse). A larger outfit is Potsdam per Pedales (748 0057; per day €8-12), which is headquartered at the Griebnitzsee S-Bahn station (open 9am to 6.30pm, Easter to October) and also has offices at Potsdam Hauptbahnhof and Wannsee stations (both open 9.30am to 7pm, May to September).
For a taxi, ring 292 929 or 0800-292 9298.