From Sorrento, you can travel to Positano by bus or by ferry. My friend and I opted to take the bus as we had been using a museum pass which included free bus travel. Be warned, the buses operate roughly every hour - and I mean roughly. As a result. the buses are absolutely crammed when they reach the bus stops, so be prepared to stand with someone's armpit in your face for most of the duration - think you're on the London Underground during rush hour and you've got the next nearest experience! Travel aside though, the pain is worth it.
Collegiate Church of Santa Maria Assunta is situated in the Centre of Positano and looks rather ominous when you stand below it to take a photo.
If you like shopping, there are a wide number of shops dotted up and down the roads and steps. Take plenty of money with you as you're bound to see something you like.
My friend and I headed down to the beach for some rest and refreshment. There are a number of little places you can visit to grab a drink and a snack if you would like. The beach itself seems very pleasant but can get rather crowded at peak times.
If you head off to the right, you can access a pathway which takes you to another beach around the corner. It is well worth the trip as it is quieter and has its own fort to guard you while you sunbathe.
If you would like some hints and tips about Positano and the Amalfi Coast, try this website. It has a range of locations and ideas, plus bus and ferry timetables.
http://www.positano.com/
Next time - the Villa Oplontis