Don’t eat at restaurants that directly overlook some tourist area (for example, Piazza San Marco in Venice). That desirable location is reflected in their rent, and they are going to pass that cost on to their customers. You’ll find better prices and at least as good food a block or two away.
If a restaurant has a trilingual or quadrilingual menu, it probably caters mostly to tourists, and the food probably isn’t very good. It might be overpriced, too. Restaurants that cater to tourists do not count on repeat business.
Eat Italian food, food of the specific region where you are where possible. Drink Italian wine. It will be cheaper and better than most of the rest of what’s on offer. There will be familiar restaurants, but don’t eat at them. It seems kind of silly to invest all that time and money into going to Italy and then eating stuff that you could get just as easily at home.
Coke or other sodas are expensive. Don’t expect free refills.
If you ask for water, you’re likely to get bottled water, which you will have to pay for. It might be mineral water, some of which tastes nasty (at least IMO). If what you want is tap water like you’d get at home, you have to tell the waiter or waitress that. The tap water is safe to drink.
Service in restaurants is slower there than it usually is in the US. Keep this in mind.
You will probably have to ask for the check when you are ready to go. The word for that in Italian is “il conto”. The sign for it if you’re not confident in your ability to say this is to hold up your left hand like a notepad, and make writing motions on it with your right index finger.
People eat dinner later than most Americans do. A lot of restaurants won’t open for dinner until 9pm. If you go in then, you will probably feel like you would if you went to a restaurant for dinner at 4:30pm here.
Eat at a Brek restaurant sometime, particularly if you’re in a place that isn’t known for the local food. Brek is a self-service restaurant chain, and it’s good. This is a good bet if you don’t want to or can’t spend a lot of time seeking out a good local restaurant.
They take credit cards in Italy, for the most part. I didn’t have any trouble finding places that took Visa or Mastercard- American Express or Discover might be another story. Your ATM card may not work as a debit card, but there are ATMs that it will work in. You don’t need traveler’s checks. Get cash at an ATM, or use credit cards, rather than exchanging cash at the airport or at a bank. You’ll get a better exchange rate.
You won’t have trouble finding people who speak English, unless you go way off the beaten path (not something I’d really recommend for your first overseas trip).
How do you feel about sharing a bathroom with other hotel guests? If this sounds totally unacceptable to you, you want to look for the word “ensuite” or “private bathroom” in hotel listings. Don’t assume a private bathroom for each guest is the default- it isn’t in Europe. You probably won’t have too much trouble finding a hotel with private bathrooms, but not all of them have it. If you do stay in a room with a shared bathroom, be considerate. This isn’t the time for marathon baths or showers. You are keeping other guests from being able to use the toilet if you do so.
Don’t fly through Heathrow if you can help it. Every time I’ve flown through Heathrow, I’ve had a bad experience. It is the LAX of European airports.
Take something other than shorts and sleeveless tops. You might not be allowed into some of the churches if that’s what you’re wearing, and some churches have some cool stuff in them.
Take comfortable shoes. There isn’t parking close to a lot of the places you’re probably going to want to see.
Don’t drink and drive. The DUI limit in Italy is lower than it is in the US (.05 rather than .08).
Can someone in your group drive a manual transmission car? They’re more common in Europe than they are here. If you want an automatic, you’ll have to make that clear with the car rental company.
Drivers in Rome are insane.
Don’t try to take an American hair dryer and use it with an outlet adapter. The wattage on them is higher than most adapters can handle, and I’ve never gotten a hair dryer to work well with an adapter. Don’t expect to have a hair dryer in your hotel room, either. Buy an Italian hair dryer when you get there, if you need one.