So many people telling you to validate your ticket before boarding. We will be going from Naples to Sorrento. Where do you validate your ticket?
Look for the yellow boxes marked "Convalida", they are at the entrance to each track. I tell people to allow themselves a little extra time if they can because it has happened t me a few times where I had to run to catc ha train and when I went to validate, the machine was out of order and I did not have time to use another one. The train dudes are not very lenient these days.
The little yellow boxes are being replaced by gray/green or gray/blue ones. In any case, they will be located at the platforms in railroad stations. If you are taking the Circumvesuviana from Naples to Sorrento, there may be a turnstile instead of a validation machine - just run the ticket through and it will pop back up. Be sure there is a line of text with the validation information, and keep the ticket with you until you exit the train station in Sorrento.
Since the ticket can be used at any time, it is a time stamp on the tickets that says the ticket is now good for a limited number of hours. Look around, you should see other travelers doing the same thing.
Thanks to all for the replies. I greatly appreciate it.
On the off chance that the validation boxes aren't working OR you forget to validate until after you're on, you can self-validate by writing the day and time on the ticket with a pen. If/when the ticket agent comes by, you can explain that you forgot to stamp it or that the machines weren't working. This is ONLY a backup plan, as you'll be at the mercy of the agent whether to accept it or not, esp. if you just plain forgot. But it's better than nothing.
You will be riding the Circumvesuviana line, which is a private railroad company and not part of the national system. Be sure to keep the ticket until you leave the station in Sorrento, as someone already said. We have seen inspectors stand at the exit and ask to show your ticket.
sue, You might find it helpful to have a look at this excellent website: http://www.roninrome.com/transportation/leonardo-express-the-trenitalia-nonstop-train-to-the-fiumicino-fco-airport If you scroll down to "3", you'll see a photo of the Convalida (validation) machines at FCO. Some of the newer machines are blue & gray, and more of an "oval" shape. NOTE the large red sticker on the front! Cheers!
Never be shy about asking for help, whether it's looking for the validation boxes, or verifying that you're getting on the correct train! I'm officially jealous of you and your trip ;-)