There are only two ways of travelling between Civitavecchia and central Rome: By private car or by train.

Private car with driver (€130 upwards per car): There are a number of companies that provide this service. One which is reputable and much recommended on TA is RomeCabs.

Train (€4.50 per person - each way): There are two or three local trains each hour between Rome Termini (main station) and Civitavecchia. In central Rome, these trains also stop at Tuscolana, Ostiense, Trastevere, and San Pietro stations. The cost is €4.50 each way per adult, and the journey takes just over an hour (50 min. to San Pietro station). There are no seat reservations and tickets cannot sell out. Before you get on the train, you must time-stamp the ticket in a yellow machine at the station. There is a day pass available in the station, called the BIRG ticket costing €12, which covers travel to and from Rome, and also gives you unlimited use of buses, metro, and trams (streetcars) for the entire day in Rome.

Note - these are commuter trains. They are great during non-rush hours, but are packed during rush hours, and can be difficult to get on, especially if you travel with kids or elderly.  As indicated above - the tickets cannot sell out i.e. they can sell more than capacity.

Also note for cruise passengers, you can pick up shuttle provided by cruise from ship to gate (a long walk otherwise) and walk the remaining 4 to 5 blocks. You can also buy round trip tickets from vendors along the entrance to Fort (gateway to cruise terminal), and not just at the train station.

Fast train (€9.50 to €19.00 per person - each way): There are a few faster InterCity trains between Termini and Civitavecchia, costing €9.50 in second class and €12.50 in first class and stopping only at Roma Ostiense between Termini and Civitavecchia.  There is one of these trains suitable for day-trip cruise passengers which leaves Civitavecchia at 09.19, but no other fast morning fast trains in that direction. There are also a few Frecciabianca trains which cost €13.50 in second class or €19.00 in first class. These trains do not stop at other stations in Rome. All seats on InterCity and Frecciabianca trains are reserved, and the seat reservation is included in the cost of the ticket. The journey takes 45 to 50 minutes. The BIRG ticket is not valid on these trains. 

For all train times, see Trenitalia but note that costs of the local trains are not shown more than 7 days ahead. 

Express 40 min. train for Cruise travelers (€16,50 - Round Trip, €8,00 one way): Takes 40 minutes each way.  This dedicated train was introduced in 2011 for those that want to take a day trip to Rome from Civitavecchia. It has a limited schedule (departs at 09:30 from Civitavecchia and arrives at San Pietro Station at 10:10; then returns from San Pietro station departing at 16:40 and arrives at Civitavecchia at 17:20). Dedicated onboard personnel will provide assistance and walk travelers from S. Peter Station in Rome to the Vatican. It does not run every day, as it is intended for cruise passengers. Online bookings are available at www.smartcruisetours.com (2012 season from June 1 to October 28).

For this journey, you have the same choices of private car or train. For private car, see above. By train, take the FR1 suburban train (not the Leonardo Express) from FCO towards Rome and get off at Trastevere, where you change to a local train to Civitavecchia.

Some people claim it is cost-effective to rent a car at FCO and drop off at Civitavecchia (or the other way round).  This seems unlikely, but one can get rental costs from an agency such as AutoEurope.