By plane:
Leonardo da Vinci Fiumicino Airport: board the "Leonardo-train" (departure every 30 min.) to the "Termini" central rail station in Rome.

Take Metro A in the direction of Anagnina. Get off at San Giovanni, then on foot to the Piazza Santa Croce in Gerusalemme (500 m).

Alternatively, from the Termini station take Bus N.° 649 getting off at the stop for Via Santa Croce in Gerusalemme.

By train:
From the Roma Termini station, take Metro A in the direction of Anagnina. Get off at San Giovanni; then on foot to the Piazza Santa Croce in Gerusalemme (500 m).

Alternatively, from the Termini station take Bus N.° 649 getting off at the stop for Via Santa Croce in Gerusalemme.

Train schedule can be easily found at this website.

By car:
From the ring-road motorway, GRA (Grande Raccordo Anulare), you have two choices:

1) Exit 14, take the "tangenziale" highway alongside motorway, direction San Giovanni to its end. At the trafic light, turn right. After passing the Roman arch, Santa Croce in Gerusalemme is on your right.

2) Exit 27, take Via Cristoforo Colombo and follow it to its end; pass the Roman Arch and reach the Baths of Caracalla. Pass the church of San Giovanni in Laterano, take Viale Carlo Felice to Santa Croce in Gerusalemme.