Rome is a different breed of cat. First the existing subway lines (there are only 2 currently operating and 3 more building) are very limited and few go anywhere near the major sights. Exceptions are St Peters & Vatican City (Octavianno), The Colosseum & Forum (Colesseo), the Spanish Steps (Spagne) and the Appian Way. Spend your preparation time learning to buy Rome bus tickets (also good on the metro) and how to navigate the bus stops. Google "bus tickets and routes in rome" for some outstanding how-to tutorials. You'll be cooler and walk much less. Since everything (sooner or later) goes through Termini (the main train, metro, and bus station), you can never really get lost.