Terravision, EasyJet's transport partner, operates a service to Termini, departing 30 minutes after your flight lands (irrespective of delays). It takes about 70 minutes. Tickets: €7 single, €12 return. Check return times at the ticket booth.
Holiday Taxis (easyJet.holidaytaxis.com) take you from home to the airport, then city or destination.
Visit the Europcar desk on arrival for special easyJet inflight rates.
There is a taxi rank outside the airport entrance. It should cost exactly €40 to the centre in a City of Rome licensed cab and €60 in a Fiumicino municipality licensed cab.
The Leonardo Express leaves for Termini station every 30 minutes from 6.36am-11.36pm. Tickets: €11. Metropolitan FM1 trains to Roma Tiburtina run from 5.57am, every 15 minutes from 6.27am-7.57pm, then every 30 minutes until 11.27pm. Tickets: €5.50. The journey takes 30 minutes to Roma Ostiense (with a connection to metro line B) and 45 minutes to Roma Tiburtina.