The city centre is easily covered on foot and for newcomers to Oslo, guided walking tours might be a good way of taking in the sights as well as to familiarize yourself with your new surroundings.
For more information on road safety and traffic rules, see Trygg Trafikk.
Travel on the buses, metro and trams all utilise one ticketing system. Find your recommended route here.
Airport express buses:
Airport express train:
Ferry to Denmark, Germany and Sweden.
Ferry to Denmark, Germany, Poland.
Guest harbours in Oslo
More information here.