At the table
Pizza al taglio, and buying food by weight
Point at the tray, say how much you want, and it is cut, weighed and priced by the etto. The best lunch in Rome costs whatever you decide it costs.
Pizza al taglio is pizza baked in long rectangular trays, cut with scissors or a blade, sold by weight and eaten standing or walking. It is Roman by origin, it is everywhere, and it is the answer to lunch when you do not want to sit down for an hour and a half.
It is also the thing visitors most often walk past, because the ordering works differently from anything they are used to.
Sold by weight, which is the whole mechanism
Prices are per etto, a hundred grams, and they are posted per tray because a tray of potato and rosemary and a tray of mortadella cost different amounts.
The transaction goes like this. You point at the tray you want. They put the blade or the scissors down on it and look at you. You say così, like that, or you move your hand to show more or less. They cut, weigh, and tell you the price.
Nobody expects you to order in grams. The hand gesture is the standard interface and it is used by everyone. If you want to speak, un pezzo piccolo or un po' di più will do everything you need.
What to expect on the trays
Pizza bianca is oil, salt and rosemary and nothing else, and it is the one to try first. Pizza rossa is tomato with no cheese, which surprises people and is correct. Patate is thin potato slices with rosemary. Margherita, mortadella in a split piece of bianca, and whatever the season has brought: courgette flowers, artichokes in spring, pumpkin in autumn.
The trays turn over through the day. What is on the counter at 12.30 is not what is there at 16.00, and the good places bake continuously rather than laying out the day's stock in the morning.
It gets reheated, and it should
Say nothing and it will usually be warmed in the oven for a minute before it is wrapped. If you want it hot, me lo scaldi asks for exactly that. Cold pizza al taglio is a fine thing on a bench in a park, but the crust is better warm.
It is wrapped in paper, folded once with the topping inside, and handed to you. You eat it out of the paper.
Standing, walking, or a bench
There is rarely anywhere to sit and no expectation that you will. This is food to eat on your feet, which is also why it costs what it costs: you are not renting a table, so none of the coperto and service arithmetic applies.
Some places have a shelf along the wall and a few stools. Use them if they are there.
The other counters worth knowing
Tavola calda is the same idea applied to cooked dishes: trays of aubergine, roast potatoes, meatballs, lasagne, sold by weight or by portion and eaten at a counter. Rosticceria and friggitoria are the fried version, which in Rome means supplì, rice croquettes with a thread of mozzarella through the middle.
All three fill the hours when restaurant kitchens are shut, which is most of the afternoon. See when Italians eat.
How to tell a good one
A queue of people who are visibly on a lunch break. Trays that are half empty at one in the afternoon and refilled from the back. Pizza bianca that is blistered and irregular along the top.
And no photographs of the pizza on the window, which is a sign the pizza is expected to sell itself to people who already know what it is.