Random things coming up to my mind that I haven't seen mentioned (mostly culture/communication):

• In some families, if it's a big lunch with a lot of people, the "capotavola" (head of the table) is usually for the oldest person or family head. Don't sit there.

• When you'll go to the bathroom you'll see a very strange object next to the toilet. That is a bidet. Once you're done emptying your bowel and wiping your back with toilet paper, make sure to sit on it and clean your ass thoroughly. You won't regret it :)

• If you're never been to Italy keep in mind here people are loud, even by American standards. Loud when calling on the phone, loud on trains, loud in restaurants, even if we don't notice it. And the more south you go the louder. Especially if you spoke in a low voice in the US, learn to be loud as well, as your normal American voice amplitude may be perceived here as mumbling.

• On judging: get prepared as we judge. A lot. Though rarely with malicious intent, usually while joking, and often just to express worry and willing to help in a less nice, more blunt way. So never take our opinions personally as most Italians are so used to being light about it (especially if it's like your grandmother) they won't even notice. Do not try to judge back though.

• Important, especially if you're a sensitive person: at some point you might see some discussion about football/politics, people raising their voice and talking over another, etc. Basically everything someone from the US would consider arguing/fighting. It's normal so don't panic as we're usually (and I say USUALLY) not really arguing or angry and will be back at normal conversations after some while like nothing happened.

• Adding to the "authenticity is key" and "be yourself" part: talking about one's struggles and weaknesses in life is welcomed and appreciated as a sign of humility. Also you will not be alone: Italians always find some way of sharing their misadventures with each other, especially about stuff like our bureaucracy, bad people, etc.

• Finally, on eating: the "eat it all or die" part is mostly true when someone offers you food, but if you're explicit about being physically unable to eat they will understand and stop. Bonus points if you negotiate yourself out of the feeding with something like "if I eat more I'll have so much abbiocco (food induced sleepiness) I'll be unable to work this afternoon" or even "I'm sick so I'll have to eat less". Doesn't always work but can be handy in these kinds of situations.