TIP
A tip (often called a gratuity) is a sum of money customarily given by a customer to certain service sector workers for the service they have performed, in addition to the basic price of the service.
Abroad there are countries, like in the United States, where tipping (tipping credit) is an obligation, and this is also paid by credit card, choosing whether to leave 15-20-25% at the end of the service.
In Italy tipping is neither compulsory nor customary, since the service is already included in the cost of the service.
Leaving a tip in Italy is not compulsory, but it is a reward for those who work hard and are committed to making everything perfect, especially in services where the relationship with the customer counts a lot, as could be a bar, a restaurant or even a hotel.
AT THE RESTAURANT
To tip the restaurant you can be elegant enough to do so by rounding up the rest.
If they have not collected the typical tray with the receipt, you can just leave the money there, always rounding up in excess.
But the first rule is to never be stingy. In a world where the crisis is very present, if we have the pleasure of being able to eat a good thing, with good service and kind people, a few euros more for the tip will not be an economic problem, even a small amount of money can be appreciated.