Italian tap water is sometimes heavily chlorinated so it is best to drink bottled water. Mineral water is available in all flavors: gassata (bubbly), naturale (non-bubbly), and semi - gassata like Ferrarelle (somewhere in between).
Italians usually order their food as it is on the menu seldom making special requests such as "hold the mayo".
Spaghetti, virtually the national food of Italy, should be eaten with a fork rolled against the dish. Use a spoon if you must, but cutting your food up into little pieces is considered tacky.