Basic things to know to rent a car in Europe for North Americans
Europe has all the major car rental brands. I used Hertz. Picked up from the Milan Centrale railway station. Avis and Europcar are the other two big ones I saw
If you're not from EU, you'll likely need to get an International Driving Permit as well as your regular driving license in order to rent a car here. Getting it is pretty easy. In the US you go to your local AAA branch. In Canada you go to your local CAA branch. They processed it for me in less than 30 minutes
They don't have that many cars with automatic transmission in Europe. And the daily rates of automatic cars will be more expensive than manual cars
A lot of cars use diesel instead of gasoline (diesel is also called gasoil, a term that I saw a lot of spelling variations of while driving there). Make sure you confirm with the rental agency if your car runs on diesel or gasoline
Don't get a big car. Gas is expensive in Europe and roads are narrow and winding
There are also a lot of toll booths on the highways. Cash is preferred, but I paid by Visa for most of them. I ran into one issue at a toll booth close to Montpellier with my credit card, so have some Euros on hand just in case
Some traffic rules to keep in mind
With the exception of UK, everyone else drives on the right hand side of the road
Turning right on a red light is generally not allowed unless signs clearly indicate otherwise. This is very different from North America. So just assume you aren't allowed to do it unless you see a sign or see other drivers do it
Don't drive on the inner lane on highways unless you're overtaking someone. This rule is generally not followed in North America but I noticed that it's pretty strictly followed in Europe (at least in Italy, France and Spain)
European highway speed limits are higher than in the States, and I saw people driving pretty fast (130-140km/h seems to be the norm on their highways)
But, be careful there are a lot of speeding cameras on the highways! I didn't run into a single cop while driving there but I got 2 speeding tickets mailed to me in LA after I got back. One from France and one from Italy for a total of ~200 euros