The main airport is in Girona which is the destination for Ryanair, transavia.com and Wizzair. Alternatively, you can fly into Barcelona's El Prat airport. Girona can also be reached by train.
If you want to explore alot of the coastal cities then renting a car is your best option. There is regual bus service between the towns but nothing compares driving along and stopping where you like.
The unknown gem of the Costa Brava is Tossa de Mar. This beautiful little fishing village is one of the least developed on the northern Spanish Mediterranean coast. Tossa is still a fishermen's town, with the quaint very-narrow cobblestoned streets, white houses, and beautiful coastline. Tossa also boasts some very well-preserved medieval ruins -- including walls and towers which protected the town between the thirteenth and sixteenth centuries.
If you like casinos and more luxurious accommodations, go to Lloret de Mar. However, if you prefer the less developed beaches, and don't mind less ostentatious accommodations, Tossa de Mar is for you.
Also see Girona - old city and Jewish quarter, Cadaques - Dali museum and marine park.
There are scuba diving outings to the "Islas Medas" National Reserve Park from L'Estartit. Cadaques also has various dive shops to explore the area.