If you would like to eat a good pizza (ok Italians, I know it is not Napoli) any pizzeria in Via Mazzini in the center of Turin will be a wise choice. Make sure it has a 'forno a legna' (an oven where the pizza is cooked by fire wood and not with an electric oven). Generally, it is not necessary to make reservations for a pizzeria but it is a good idea if you are numerous or if it is Saturday night. Many of these places also have restaurant service so if you are not in the mood for pizza you can order something else from the menu. If you need the names of the places just read on...
In via Mazzini there are 3 good pizza places: Spaccanapoli, Stua, and Birreria Mazzini.
I would also like to suggest some other pizzeries in Turin which my stomach has found quite satisfying. Here goes: La Stadera which is nummy and also near Parco Valentino so after dinner you can go on an evening stroll and burn those calories. Area Nova which serves pizza with only Mozzarella di bufala (buffalo mozzarella) and has a very inviting environment. And last but not least (and I think most people from Turin would agree with me on this one), I Quattro Soldi which has everything to choose from. You should see the appetizers and the desserts. I had a hard time making up my mind. Of course the pizza and main courses are delicious too. Service is good in all of these places. I have personally tried out every place I am suggesting and I have what the Italians call a good fork (una buona forchetta). In other words I can distinguish good cooking from bad cooking. I have not included prices but most pizzerias are extremely affordable compared to restaurants.
Favorite Dish: There are a variety of excellent pizzas to choose from but my all time favorite is as follows: fresh tomato (pomodoro fresco), buffalo mozzarella (mozzarella di bufala), ham (prosciutto), and arugula (rucola). You can then top it off with a bit of olive oil just before eating it. This exact pizza may not be at every pizzeria but if you smile really nice at the server you could probably get the ingredients you want. It never hurts to ask. A small warning to the Americans out there. Each person normally orders their own pizza and they expect you to eat it all. There are no doggie bags in Italy. It's better to just leave it on the plate if you can't finish it. If it is really too much (peek at your neighbor's plate before ordering) order one pizza and ask for an extra plate. Then you can split it with your dinner partner.