Clothes, in the evening it gets cool and dark. Well, seriously. Please check out the weather forecast and bring something appropriate. You don’t need any elegant dress. Beach flip-flops and good running shoes are important. Snorkel mask, perhaps.
Tipping is expected in the restaurants frequented by foreign tourists. The waiters in these restaurants know very well what is common in your culture. You should know, though, that an Italian usually only pays what is printed on the bill. Importantly, they are considering whether the amount is justified. You can also ask for a proper invoice, which you can also get if you suggest that you need it for business. Speak calmly in your language and use your hands to make it clear what it is all about. If you stay friendly, then it all works out too. By the way, you are legally obliged to take the receipt with you. You may be checked by finance police outside the door.
Italians pay in the restaurant at the checkout when they go out. Money is dirty and shouldn’t actually change hands at the table. Of course, the waiters also adapt to the visitors and you can also have it the way you are used to from home. But it is better you go to the cashier near the entrance. In particular, if you pay by card, want a special receipt and maybe another brandy.