It's a bit odd asking a question about Italy in a forum group for Japan but here's some information that might assist you:
Many have said to use the rail/train systems as they are fast, convenient and hassle free for the most part. Renting a car and driving is a headache and you encounter gridlock in certain parts.
ItaliaRail - Italy Train Ticket and Rail Pass Experts
Ferrovie dello Stato - Homepage
Here's more travel tips that you should read:
In Italy Online - Train Tips
Trains in Italy
Culture Shock | Italy
Italy travel tips: advice for travelers to Italy