My advice is to look for the blue P (Parking) signs and find parking just outside of the centers of villages or tourist sites. Even in Pisa there are decent (though expensive) parking lots one block from the Leaning Tower. It's the same for Pompeii. Most towns and larger cities like Florence or Siena have public lots. These are affordable and safe (some are indoors or underground) and all are decent walking distance to the sites you would want to see. Of course, as a rule, don't leave valuables in the car. Some (like in Siena, Cortona or San Gimignano) even have escalators nearby that take you up to the center of the raised town. And if you are just passing through a small raised village, most have a loop road that goes up and around and back down again (circling the village center), usually with several parking lots along the way fairly close to the centro storico (historic centers).
Again, learn to recognize and respect the ZTL. When in doubt, don't go through. When in areas where you have to go through, like when your hotel is in the ZTL, don't panic. Just make sure your hotel contacts the local police to let them know your license plate number and type of car so you don't get a ticket. For example, in Matera it was impossible to get to our hotel in the heart of the old sassi section without driving through a ZTL. We gave our plate number to the hotel staff to call into the police. (Hopefully, that worked.) You can even get a special handicapped permit if you are staying inside Florence's historic center. And when you have return a car like I had to, in downtown Florence, use Bing Maps or Google Earth street view (before your trip) to take a look around at street level for the ZTL signs. Do a drive through at ground level in Earth. This is especially helpful for Florence. There is only one way IN to the car rental return garage and one way OUT. Any other streets will take you into a ZTL. Most of this is by design to raise revenues. Just educate yourself to get around the ZTLs safely.
I should mention that the ZTL zone in Florence is really big--pretty much the entire tourist center. This is one of the reasons why we opted out of going into Florence itself. We would've had to park in a lot very far from the tourist sites and either take the confusing buses or walk it. With my poor legs, that would have been a real effort. In fact, Lisa and I recently discussed that if we ever do get back to Florence we would stay inside the center to make things easier. There is so much to see in Florence that I'm sure a nice way to see it all is throttle back, not go anywhere else BUT Florence for about a week. Perhaps that's another trip...
Speeding and Speed Traps:
Well, the good news is, driving on highways in Italy is actually a bit safer than here in the U.S. First of all, the fast lane (as we call it) is really a passing lane that most Italian drivers seem to respect. If you enter the passing lane, you are expected to pass the slower traffic in the other lanes, and then to move back out of the passing lane. Guess what? They actually do it. This means if you park yourself in the middle lane and someone comes up behind you, he won't ride your butt but zoom around you in the passing lane. Just make sure you don't go into the passing lane and NOT pass. If you coast along without passing, you WILL have someone hugging your rear. Also, be aware that once in a while you'll get a speed demon blasting by everyone--but at least they're in the passing lane. Expect to be shocked once in a while, or keep an eye in your rear view mirrors so you don't get spooked. In general, keep below or at the speed limit. There are so many ways for local and regional Italian governments to catch you. Why chance it?
Now, as for the speed zones. There are basically two types of speed control technologies used in Italy. The first is cameras. They take a picture of your license plate and give you a ticket automatically. You'll never see a policeman and the ticket may take the better part of a year to get to you. There are fixed cameras--large gray boxes on the side of the road or hanging from a bridge or pole. The other type of camera is mobile and operated by a policeman sitting on the side of the highway.
GVI Driving Tip: Before traveling to Italy, check out signs on Google Earth (street view) in areas you will be traveling in. If the signs are a bit wordy, pull up Google Translate to find out what the sign says. I found this enormously helpful for finding out restrictions on parking signs, signs posting the schedule of the local market day in the piazza, etc.