Buy a map before visiting Rome by Packerman
I can't emphasize enough how important it is to have a good map. Keep it with you in a convenient place because you will probably be looking at it several times during the day. A map is also good to have just to give you an idea of how much you can see in a day and how long it should take from getting from place to place. I figure about 1 minute walking per 100 meters.The weather was great!