Take two slices of Italian bread. Stuff them with delicious goodies such as mozzarella, tomatoes, prosciutto, fresh basil, roasted red peppers, and whatever else makes you happy. Brush with extra Virgin olive oil, and press between the hot plates of a Sandwich griller for the best Italian style sandwich outside of Italy.
That is the basic recipe for a great grilled Italian sandwich. Switch out the cheese for another you like better, add some sliced olives, or spinach, or anything you like - there are no hard and fast rules here.