1. No ketchup on pizza or spaghetti or whatever. Ketchup does not belong to our culture.
2. No Latte at Lunch or Dinner, it is a big, giant NO after 11 a.m.
3. No parmesan on seafood: unfortunately, some Italians do, but then again, we had so many invaders that they are probably sons of foreigners.
4. No cutting spaghetti with a knife. If you cannot handle a fork, you should go back to primary school.
5. No cappuccino with pizza; see rule no. 2.
6. No pineapple on pizza.
7. No butter on bread, olive oil instead. This habit depends on climate; on the Italian Alps (where temperature goes down to -10°C) butter is preferred to olive oil; but 99% of Italians live in temperate regions.
8. No cheese with fish: see rule no. 3 and remember what I wrote about the paternity of some Italians.
9. No ice in wine; this rule can be relaxed in the hottest days of summer, since too much water is dangerous for your health.
10. No eating while walking: eating is a top serious activity in Italy; just as an example, a mother receiving a visit from her son after long time not seeing him, would immediately ask “did you eat?”, instead of “how are you?”.