How to get to Naples to Positano to Sorrento

As soon as you can, get hold of a copy of Rick Steves Italy (or Rick Steves Snapshot: Naples & The Amalfi Coast if you're only going to this region). It will not only have all the possible routes, but will have lots of other invaluable information about these places.

The Circumvesuviana train runs between Naples and Sorrento, and buses run between Sorrento and Positano. These are frequent and cheap. There are also boats connecting these, in season (you'll need to check if they're running when you're there, and how often).

Estella, at Napoli-Centrale train station, both the Trenitalia trains and the Circumvesuviana trains stop there. The Circumvesuviana platforms are downstairs. The Circumvesuviana train is a local train that runs frequently between Naples and Sorrento. Trip takes just over an hour. To get to Positano and from Positano back to Sorrento, it's the SITAsud bus. It's the only public transportation up and down the Amalfi Coast between Sorrento and Salerno. There used to be a ferry run but I'm not sure if that segment is still running.

If arriving at the airport, take this bus to Sorrento

http://www.curreriviaggi.it/inglese/E_index.html

Arriving by train, go downstairs in Naples station take the Circumvesuvian train to Sorrento

http://www.eavcampania.it/web/sites/default/files/ftp_orari_ferroviario/Cx.pdf

Sita Bus Sorrento to Positano

Timetable http://www.eavcampania.it/web/sites/default/files/ftp_orari_ferroviario/Cx.pdf

Ferry Positano to Sorrento

http://www.coopsantandrea.com/en/servizidilinea/servizi.asp

This 3/day card will give you access to attractions and transposrtation

http://www.campaniartecard.it/artecard_Regione.cfm

Hope this helps

Another great option of you are travelling during the day, take the train from Naples to Salerno, and hop on a ferry to Positano.....great views and very relaxing!