Rome to naples

We went to Naples Centrale train station from Rome Termini station last Sunday on the train. It takes about an hour.
You can buy a ticket out of a machine kiosk real easy there

Yep, definitely train. Roma Termini (Rome's central station) to Napoli Centrale. Schedules can be explored here:

Trenitalia (Italy's national rail service):

http://www.trenitalia.com/tcom-en

Italo (private rail service mostly between major cities):

https://www.italotreno.it/en

Price breaks are possible if ordering tickets in advance but you must be willing to make the train you book to avoid penalty.

The high speed train is the easiest to use.

If you book tickets in advance you can take advantage of huge discounts. Be aware, these discounts come with very strict rules. If you book the super economy on trenitalia and miss your train these tickets will be worthless. If you book the economy tickets on trenitalia and miss the train your tickets will be worthless as well but you can change the date and time of the ticket (for a fee) if you do it before the train departs.

Right now the difference in cost on trenitalia is super economy=16.90, economy= 35.90 and base tickets are 46.00 euros. The base price is what you'll pay at the station if you don't purchase in advance. Base is the most you'll pay for a ticket in second class on any train.

When booking train tickets I always treat them as I do airline tickets, which cannot be changed either. Give yourself an extra 15-20 minutes at the station to find the correct track and be waiting when the train gets there. They don't display the train information before the train pulls into the station so you don't need to be there much earlier than that.

Donna

Just to add that going from central Rome to central Naples, the train is far easier (as well as faster) than a rental car.

I was not the original poster but wanted to say thanks to all for your helpful replies.