If you are staying in Rome, I suggest to catch the 8:00 am train (train number 7533) from Roma Termini that arrives at Cassino train station at 9:43 am. Please, visit the website of Treni Italia for train schedules and to book your train on line.
Once you have bought it, print it and it is already validated. If you don't have a printer available, you can download it on your smart phone. The train from Rome to Cassino is a regional trains that stops several times. For this type of trains you will not have a reserved seat, you can sit anywhere. The train starts at Roma Termini and ends at Cassino train station (final destination of the journey), there will be plenty of seats as you will be traveling the opposite direction of the commuters.
he single train ticket from Roma Termini to Cassino is about 8,20 euros per person (price updated June 2020).
Do not buy a return ticket, you may catch the return train from a different train station. It depends from the chosen itinerary/route and train tickets for regional trains can be bought on the spot without any problem.If you are staying in Cassino area, I will be glad to pick you up directly at your hotel/accommodation.
If you are staying in Naples I suggest to catch the Flixbus to Cassino. You can check out the timetable here: https://global.flixbus.com/
NEWS: From June 2020 there is also the possibility to catch High Speed Trains that will stop to Frosinone and Cassino. The Cassino region is now connected with fast trains to Milano, Bologna, Florence, Naples; you don't need to change your trains and you can fast reach Cassino from many parts of Italy. Please enquire for more information, I will be glad to assist you in your planning.
For further information don't hesitate to contact me: firstname.lastname@example.org or whatsapp +393382458831