Here's city buses, metro, and tour buses which I think are the easiest to utilize. Tourist business is big and they want you to succeed. But you gotta plan ahead a bit. I was mostly interested in the Vatican/St. Peter's and antiquities...not Catholic but it's hard to argue with all that history...and have enjoyed myself a lot. I also like to see what I call "supermarket culture", how folks live here or there. Since I have to graze for chow anyway it makes it fun for me. Simple guy, I guess.

A site called The Rome Toolkit I found pretty helpful. www.rometoolkit.com