Sorrento is a wonderful place to explore and getting there can be just as much fun. For those of you who like excitement there is a Hertz rental car just outside of the main Centrale Train station in Naples. Keep in mind that they do close during lunch and re-open around 2pm. If you’re daring go right ahead and rent one, but renting a car is really not needed. Keep in mind that the traffic here is worse than Paris. They will eat you alive.
The metro/light-rail train to Sorrento costs (2009 price) 3.60 euros. This is an older train, and takes 1 hour 15 minutes to Sorrento. The train is more like the London Tube, Chicago El, or NY Subway than like the newer LightRail systems of Denver or Phoenix.
Instead of taking the train to Sorrento you can hire a limousine (Imperatore limousine). While this is a costly way to travel, taking the limousine has additional benefits. The limo provides you time to learn from the locals by conversing with your driver. They can offer suggestions as to where to eat, what to see and what’s the best time to see things. Your limo driver can tell you about the sites along the way including suggestions as to when to visit places such as Pompeii. They even offer private tours for those of you who do not want to be in a large tour group. Your luggage stays with you at all times. This is a costlier way of getting to Sorrento but it can be worth it.
Taxis can also take you from Naples to Sorrento and places inbetween or further.
Another option to look into is either a ferry or hydrofoil to get you there. The only drawback is that you have to get yourself and your luggage down to the harbour a couple of miles away but you can do this via a Taxi if arriving from the Airport or main Euro-Rail Train Station. If you are arriving by Cruise Ship then it's the same port as the ferry and hydrofoil and is a quick walk to the ferry/hyrofoil docks. If you get seasick, reconsider the ferry/hydrofoil as they travel parrallel to the waves and they can sometimes get choppy. Dramimine pills can combat this though. The limo, taxi, train, ferry and hydrofoil services will bring you to most destinations including Positano, Ravello, Isle of Capri, Sorrento, Naples, and Almafi so sit back and enjoy.