If you are not staying centrally the metro is a great way for getting into town, else there is no reason to use it as Rome is a city best crossed on foot. Under all circumstances avoid the morning and evening rush hours (7:30-10:00 and 4:30-7:00). The metro is safe and many of the trains are air conditioned. The trains run between 5:30 am and 11:30 pm (09:00 pm on the A line in 2011 for works reasons). The A line, which is red on the maps, passes through Pz. del Popolo, Pz. di Spagna and Pz. Barberini. The B line, which is blue, passes through the Via Cavor (Monti district) and the Colosseum. They intersect at Termini train station.
As a tourist the only reason to catch an urban train is either to transfer in from the Fumicino airport or go to Ostia. Ostia Antica and the sea at Ostia are both worth a trip out of town. For the later go to the end of the line, Christopher Colombo Station, and then catch the bus with “mare” (sea) on it. It stops at the “Cancelli” (the gates), all of which are interconnected on the same stretch of clean beach.
Rome’s city buses are orange; the ones travelling out of town are blue. You want the orange ones. The network is extensive with the main terminal being Termini Station. Busses are modern and in most you can now buy your tickets onboard from a machine if you have a 1 euro coin.
The downside of buses are, firstly they get stuck in the crazy roman traffic, and secondly, they have a tendency to attract pickpockets. The way to avoid this is; do not travel on them when anybody has a reason to invade your body space like during rush hour. While on the way to sports events the metro, buses and trams are packed but there is a good buzz between the fans, especially for the 6 nation’s rugby. Still keep an eye out for pickpockets and if you catch one do not be afraid to shout of “ladro” (thief) and hope you get some help to give him a good kicking.
A single trip on any public transport is 1 Euro and your ticket needs to be validated in the onboard machines or at the gates on the metro. Thereafter the ticket is valid for 90 minutes travel with one metro ride allowed. The day pass costs 4 Euro, the 3-day one 11 Euro and the weekly one 16 Euro. If you are staying out of the very centre a pass makes sense and a Roma Pass, which costs 25 Euro and includes entrances to three public monuments, makes even more sense. Another good solution is to take the special tourist buses.