You may find a good transportation system while in Stockholm but there are few tips one should keep in mind while traveling in Stockholm city:
Avoid Taxi: Step aside Taxi and try to use Public transport which is much cheaper and available for all destinations in Stockholm city.
Get Transport Passes Instead: Single zone tickets on metro train would cost 36 SEK. There are travel passes available for 72 hours card for 36$ (230 Sek) and 5 days pass just for 45$. These passes can be used for all public transportation which include metro, commuter train, public buses, some boat and ferries as well.