The old town is compact and best explored on foot — most of the main sights are within 15 minutes' walk of each other. Trams and buses cover the wider city and run frequently; a single ticket covers 60 minutes and allows transfers.
The SKM commuter rail is the quickest way to reach Westerplatte (tram 9 is the alternative) and to travel between Gdansk, Sopot, and Gdynia — trains run every 10–15 minutes during the day. A ZTM day pass covers trams, buses, and the SKM within the city zone; a Trojmiasto pass covers all three cities and is worth buying if you plan to explore Sopot and Gdynia.
In summer, boats run from the Motlawa waterfront to Westerplatte, which is the most pleasant way to make that trip.