Fiumicino: fastest options
Leonardo Express goes direct to Termini in about 32 minutes and is the easiest first-time option. FL1 is cheaper and useful for Trastevere, Ostiense or Tiburtina. Buses are cheaper but traffic-sensitive.
Ciampino: simple choices
Airport coaches to Termini are easiest. The public bus plus Metro A can be cheaper but is less comfortable with luggage. Taxi fixed fares apply only with official white taxis and within the defined central area.
Taxi and transfer traps
Use official taxis only, confirm the fixed fare before leaving and avoid drivers approaching you inside terminals. Private transfers can be useful for late arrivals or families.
Which arrival area to choose
Termini is practical for metro and trains but not always the nicest base. Prati works well for Vatican stays, Trastevere for evenings, and Monti for Colosseum access.