Amsterdam's public transport is dense enough that you're rarely more than a short walk from a tram, bus or metro stop - the trick is picking the right pass rather than figuring out routes.
The GVB network (trams, buses, metro and the free ferries across the IJ) covers the city thoroughly, and a multi-day GVB pass is usually the simplest option if you're staying a few days and moving around a lot.
Walking covers the city centre well, since most major sights sit close together within the canal ring. And if you want to travel like a local, renting a bike for a day is one of the more memorable ways to see the city - just be prepared to keep pace with everyone else on the cycle path.
