When you hang out, always be sure to bring some cash with you: in Italy this is (still) the most common and accepted way to pay. Usually bars, small shops and restaurant do not accept credit card. In any case, you can always ask before purchasing anything if you can pay by credit card or not. We say: “asking is lawful, to answer is courtesy”, which stays for asking never hurts. Credit card is always accepted in the big chains (McDonald’s, IKEA, etc.), at the supermarket/gas station, etc.
Also, tips are not needed in Italy: the cost of the service is already included in the bill, it is called “coperto” (cover).
And another very important thing to keep in mind is that splitting the bill and having each person paying at the waiter/waitress his/her part is not really a thing here. I suggest to always ask before sitting, in this way you can decide to stay or leave. Usually, for big groups, we go with “alla romana”: you split the bill by the number of people eating or drinking, and everyone puts on the table his/her own amount (by cash). At the end, one person collects all the money and take it to the waiter/waitress.