The main stations of Rome are two: the Stazione Tiburtina and Termini Station. The arrival in either station depends on the departure city, the times and the type of train, to control the information you need to take as a reference the Trenitalia website, the most important Italian company transport of iron and Italo, the new high-speed line.
Termini Station is located in Piazza dei Cinquecento and the second floor of the station you can take the subway, both Line A, Line B and Line B1 as it is the point of sharing underground, allowing you to reach all parts of the city. Also in front of the station is the terminal of many buses to all directions, from the central to the peripheral of the city.
Tiburtina Station is located in a more peripheral part of the city, in Piazza della Stazione Tiburtina. At the bottom of the train passes the line B of the metro you can reach, in addition to Termini Station, also the most points in the city. It is also at this station for trains to Fiumicino airport.
In the square located in front of the station there are many buses that take you around the city in both central and peripheral.