Rome has an integrated public transport system of metro, bus and tram. Tickets must be bought before boarding, and can be obtained from ‘tabacchi’ (signalled by a big ‘T’ sign, which are dotted around throughout the city) or from the machines or booths at major metro and tram stops. One ticket allows you on any mode of transport, and the fares are as below:
A ‘Biglietto’ is a single ticket that costs €1. You can change buses, or into and out of the metro on one journey. This is valid for 75 minutes.
A ‘Biglietto Giornaliero’ (daily ticket) costs €4 – this is valid until midnight on the day it’s purchased.
A ‘Biglietto Turistico’ is a tourist ticket, valid for 3 days. It’ll set you back €11.
Lastly, if you’re in Rome for a longer stay, then a ‘Carta Integrata Settimanale’ is a week-long ticket that’ll cost you €16.
The Rome Metro
The metro runs two lines, Linea A (Red Line) and Linea B (Blue Line). The Red Line runs from northwest to southeast, passing by the Vatican, the Spanish Steps and the Trevi Fountain. The Blue line, running from northeast to southwest, runs past the Colosseum. For full info, see the map below.
The lines cross at the central ‘Termini’ station. Trains operate from around 0530 to 2330, but run later on Fridays and Saturdays.
Rome Maps
Firstly, it's useful to have an idea of where things are in the city, and so we've found a useful map courtesy of HotelinRoma.com, a useful site if you've not found somewhere to stay, yet. Click on this link for a very handy layout of the major sights and areas of central Rome.
Secondly, having established how everything is laid out, have a look at the Rome Metro map below, as this is the handiest way of getting about the place.

General Advice
When boarding a bus or metro you have to ‘convalidare’ or validate your ticket in the little yellow machine onboard, to mark when the ticket is valid from. When using a daily, tourist or weekly ticket it must only be validated the first time you use it. Inspectors are to be found riding the metro and buses checking for tickets – keep your validated ticket on you as proof-of-payment, otherwise you risk paying a fine. Inspectors are known to escort offenders to an ATM to make them cough up, so it’s best to keep your ticket somewhere safe in case you need to produce it!
Taxis
Most Rome taxis are white, and can be found at the numerous ‘fermata dei taxi’ (taxi ranks) around the city, including Termini station, Piazza di Spagna and Piazza Barberini, and most major squares. A journey from one side of town to the other should cost no more than around €15, and a little more at night, so beware of being ripped off if you're being asked for much more.
Parking
Parking’s not the best in the very centre of Rome, so you’re better off finding one of the larger car-parks slightly further out. Termini Station and the Villa Borghese are the two most recommended, as they are the easiest to find on a map (Termini’s pretty central, the Villa Borghese is located to the north of the city centre, and is also where the free buses to the Stadio Olimpico will run to/from on matchday). Both will also be well signposted. If these are unavailable, then many of the more suburban metro stations have cheap car-parking options, but these are un-manned carparks and won’t offer the same security as the larger city-centre ones - like Anagnina and Cinecittà on Line A, or Ponte Mammolo on Line B.
Also note that there is a fine for non-residents cars entering the Centro Storico (much like the congestion charge in London) during the day.
If you have a hotel booked, it may be worth checking with them in advance, as many will have an arrangement with a nearby parking facility. Failing that, you can try the below (prices in Euro, naturally), with addresses/maps easily available through Google maps:
Termini Station, ES Park, Via G. Giolitti 267, tel. 0644704053. 450 cars, first two hours cost 1.50 per hour, then 1 per hour, 13 for 24 hours, open 05.00-01.30
Terminal Gianicolo, Piazza Rovere, tel. 066840331. 723 cars, 1st-5th hour costs 1.30 per hour, then 1.10 per hour, 25.90 for 24 hours, open 06.00-01.30.
ParkSi Villa Borghese.Viale del Galoppatoio 33, tel. 063225934. 1,800 cars, 1st-3rd hour costs 1.15 per hour, then 0.90 per hour, 14.45 for 24 hours, open 24 hours.