You see quite a hump in the summer temperatures in Rome. It's no wonder Romans leave the Eternal City in August.
Even if the high temperatures don't scare you, let me remind you that with all the asphalt and big stone buildings retaining the sun's heat, hot nights spent in a hotel room that's not air conditioned can feel many degrees hotter than the outside temperature.
Without fail, Romans recommend that the best time to travel to Rome is from mid-September to October. Yes, it might rain, but the temperatures turn out to be quite nice, even if it is getting a tiny bit chilly at night. Almost no one recommends November, but I've had very good luck the last few years with weather in the first half of November.
May has almost the same temperatures as October, and April, while you're likely to feel chilly at night, is almost as good. March weather is really changeable, becoming more stable in April.
Rome has two airports. The largest is Fiumicino, but Ciampino handles a lot of traffic from inside Europe. The Aeroporti di Roma site gives information on both.
For budget airlines that serve Italy, see: Italy Low Cost Airlines
To get to and from Civitavecchia from Fiumicino, see: Civitavecchia to Rome Transportation
To get from Fiumicino into Rome, see Rome Airport to Central Rome Transportation
Fiumicino Airport Hotels (FCO)
Ciampino Airport Hotels (CIA)
You can get tickets to all attractions when you arrive in Rome, of course. Many people like to have them in advance, thus avoiding long lines, especially in the summer and fall season. Select Italy is a reputable company that sells tickets to many museums and events in Italy. Here are some links for Rome:
Map of Rome: Interactive, zoom in and out.
Street Map of Rome: see Rome street by street
Hotels in Rome are Expensive. Our favorite places to stay are the Daphne Inn, for its helpful staff and good location, and the Hotel Residenza in Farnese [read a review] for its quiet location near the Camp di Fiori.
Friends back from Rome highly recommend the cheaper Hotel Licrico. Another hotel we like near termini is the Des Artistes.
Another alternative that really appeals to us, is to rent a villa or apartment in Rome. See Select Italy's List for more. It's not as expensive as you might think, and villas don't have to have hundreds of rooms, either. Also see: Rome Hotels - RomeBy.Com