It is an absolute given that you will be eating out when traveling through Italy. Choosing your dining experience depends on what you're hungry for, and how much time you want to spend eating. The choices seem simple: pizzerias, trattorias, caffes, and restaurants. If you're craving a Big Mac and fries, McDonald's is becoming the 'international fast food' chain, and can be found in certain Italian towns. Yet what about grocery stores, sandwich shops, and station vendors?
First word of advice: avoid train station vendors, unless you prefer food with the consistancy of cardboard. This advice can be given for some caffes and vendors located near tourist spots. No matter what kind of hurry you're in, inspect the food in display cases: if the bread does not look freash, the cheese looks hard, and the tomato sauce is bright red, it'll probably be a wasted experience.
With warning issued, we'll start with breakfast. The Italian breakfast tends to be on the lighter side, and an assortment of pasteries or cantouchi are available in several cafes. If you rise early enough, you may purchase pasteries, still warm from the oven, at the local bakery. Some hotels offer breakfast with the stay, especially if you're traveling in a group. It's often simple fare; you may need to enjoy a 'second breakfast'. A tasty option is to purchase individually wrapped packets of Mozzerella di Buffala at grocery stores--they make excellent breakfast for those who want something more substantial than a pastery. Very refreshing, this is literally a ball of white mozzerella cheese packaged with water. I suggest taking it back to your room, though--few Italians eat 'on the go'.
Which brings us to lunch options. As you're walking though town, choosing your 'pranzo', you'll notice walk-in sandwich/pizza shops. "But it was said Italians don't eat on the go!" And they don't--they find a place to sit down before they begin eating. I recommend a foccacia sandwich; flat bread baked with fillers (pepporoni, cheese, or spinach), heated in an oven before being served.
The sandwich shops are located on side roads; in Florence, I followed my nose down an alleyway I would never have ventured, and discovered a wonderful sandwich shop. While on the topic of sandwiches, it needs to be pointed out that a few grocery stores custom-make sandwiches in the ‘deli’ section (note: the deli section in Italy is vastly different from our own. Grocery stores are usually very small.) In such places, there is a variety of breads and fillings to choose from; cheeses, eggplant, tomato, proschutto, plus more. Mayonnaise is not common, nor is peanut butter or ketchup…it‘s best to leave those at home.

Trattoria’s are informal restaurants (closest comparison is Applebee's; and that's a stretch); when the weather is warm, seating is available outside. The menu fare ranges from calzones and pizzas, to pasta dishes and salads. Prices range as well, depending on the location: the closer to a tourist spot, the more expensive the price. Smaller trattorias are found down a side road. This is probably where you’ll find the locals, and better food. Larger trattorias combine a bar, caffé, and restaurant--my experience in such places was always positive.
After lunch, in either restaurant, trattoria, or caffé, comes dessert. In the summer, dessert is called gelato. Italian ice cream; smooth, freshly made, with natural ingredients. Whereas American ice cream is made with milk, Italian ice cream--gelato--is made with a thick cream. This makes for a fuller taste, enhanced by the natural fruits and flavors. Prices for gelati range from the very expensive gelatteria near Piazza Nuovu in Florence, to reasonable summer choices at a local caffe. Visiting Venice, and gelato is not your choice? Well, there’s always the Haagen-Daaz ice-cream shop.
Supper can be had in a trattoria, but will more likely be in a restaurant. There is a growing trend of restaurants extending their seating outdoors in the summer, but most only have interior seating. Menus are posted outside the door; here, you can check the choices and price-range. The choices usually encompass: antipasta (appetizers), saletta (salad), pizza, pasta, primo corso (first course), and carne (meat), not to mention desserts. I suggest something different every night; things that may have been questionable in the states can have an ethnic appeal in Italy.
Just remember; you are in a foreign country. Enjoy what they have to offer!