As an Italian from Naples these are the basic rules here.
(Reposting an older comment of mine)

• Roundabouts:
  - How it should work: Give priority to people already in the roundabout.
  - How it works in Italy: Slowly approach the roundabout and throw yourself in there at the first occasion. Other people will stop or crash. It's a dare.

• Pedestrian Crossing:
  - How it should work: Stop your car when a person is crossing the street.
  - How it works in Italy: Use your air horn, signals and accelerate. The person will run faster and move out of the way.

• Signals:
  - How it should work: Use the signal to let other drivers know you are about to turn.
  - How it works in Italy: If you don't know where to go use your signals randomly. You can use the left signal, then start a turn on the right, then change signals. The drivers behind you will get scared and slow down, giving you time to find the right street you're looking for.

• Parking:
  - How it should work: Park only if there's a spot available. If someone else is already parking find another spot.
  - How it works in Italy: If there's not a spot park your car anyway. When the other car needs to get out it will start asking for you. The 'Use-the-signal-to-claim-a-spot-that's-about-to-be-available rule' doesn't apply. When you see a spot the fastest one gets it. If you lose you can establish dominance by getting out of the car and start screaming and insulting.

• Traffic lights:
  - How it should work: Green = Good to go. Yellow = Slow down. Red = Stop.
  - How it works in Italy: Green = Go. Yellow = Accelerate. Red = Go. Other people will stop. Corollary: If someone has stopped with a red light start honking and flashing him to let him know how dumb he is. Make your point clearer by screaming as well.

• Motor-scooters:
  - How it should work: One or two persons depending on the size of it. Wear your helmets. If there's traffic you can overtake on the left when allowed.
  - How it works in Italy: Fun for all the family ! Bring your children, grandparents, there's room for everyone ! No helmets, they're for losers. Let your toddler enjoy the view by putting him between you and the windshield. If there's traffic use the sidewalk ! Fast and easy !
  (Edit: I'm not even joking)

Final edit: This is just a taste