Booking train tickets on-line

It is a good idea to book train tickets in advance on-line if:
1) It will get you a cheaper price by booking earlier.
or
2) You will not have time to buy them at the station.
The disadvantage of booking earlier is that the tickets will only be valid on a specific train. You must decide when you buy the tickets which train on which day you wish to travel on.

• Italian High Speed trains must be booked. Your ticket will include a reservation with the date, time, train number, carriage number and seat number.
• Italian Regionale trains have no discount for buying in advance, and no booked seats. On these trains there is no advantage in booking in advance. It is just as simple to buy a ticket at the station. These tickets must be time-stamped before you board the train.

For Italy, the main train operator is www.trenitalia.com You can book tickets for most trains in Italy at this site.

There is no reason to book in advance if you are concerned about the train being sold out. The ONLY reason to book on-line is to take advantage of any discounts available. The discounts can be substantial but you are then locked into a fixed schedule with no or limited exchange options. Use trenitalia.com

Ditto to all of the above. For travel between certain Italian cities, also check http://www.italotreno.it/en.

Also be aware than some journeys - such as Naples to Sorrento - involve local commuter trains which aren't operated by the national Trenitalia system so those won't show up in a search on that website. Local commuters, though, are inexpensive, never need booking in advance, and tickets easily purchased at the stations on the day of the journey.