At the table
The bar, and the two prices
Pay first, then order, and drink it standing up. Sitting down at the same counter can cost three times as much, legally and openly.
An Italian bar is not a pub. It is the place you have breakfast, buy a coffee at eleven, take a sandwich at lunch and drink a beer at seven, and it is open from before dawn until late. Learning to use one is the single most useful thing a visitor can do, because there is one on every street and most people never go in.
Pay first, then order
In most bars, particularly busy city ones, the order is: go to the cassa, say what you want, pay, take the scontrino, and put it on the counter with a coin on top so it does not blow away. Then say your order again to the person behind the bar.
Doing it the other way round, ordering first at the counter, works in a quiet neighbourhood bar and stalls in a busy one. If you cannot tell which kind you are in, watch one person ahead of you. It takes ten seconds and it answers the question.
Standing costs less, and the difference is not small
Al banco, standing at the counter, is one price. Al tavolo, sitting at a table, is another, and the table price can be two or three times the counter price for the identical cup.
This is not a scam and it is not aimed at you. The prices are required to be displayed, usually on a laminated sheet near the till, in two columns. Read them off that sheet rather than trusting a figure from a web page: they vary by city and by how good the view is, and they drift, so this guide does not quote an amount it would only have to keep correcting.
Neither is wrong. Standing is what most people do most of the time, and takes about four minutes. Sitting buys you the table for as long as you want it, which in the right piazza is worth every cent. What catches people out is doing the second while expecting to pay for the first.
Note the two-step version of this, which surprises even people who know the rule: in some bars you may order at the counter and then carry it to a table yourself, and be charged the table price anyway, because the price is for the seat and not for the service.
Breakfast is small, sweet, and quick
Italian breakfast is a cornetto and a coffee, taken standing, in under five minutes. The cornetto is not a croissant, whatever it looks like: it is softer, sweeter and usually filled, plain (vuoto), with apricot jam (albicocca), with custard (crema) or with chocolate.
There is no savoury breakfast. There are no eggs. Asking for them marks you out more reliably than anything you could order later in the day, and a bar that offers a full English is a bar that has noticed the tourists.
Words that get you what you meant
Un caffè is an espresso, always. Un caffè macchiato is an espresso with a splash of milk, and is a different drink from the large milky one that word means elsewhere. Un cappuccino is breakfast, though see the coffee guide for how firm that rule actually is. Una spremuta is fresh-squeezed juice, usually orange, while un succo comes from a carton.
For water, naturale is still and frizzante or gassata is fizzy. If you just ask for water you will be asked which, and it is the fastest question in Italian hospitality.
The bathroom, and the unspoken deal
Bar bathrooms are for customers, and this is understood rather than policed. Buy something, even a coffee at the counter, and the bathroom is yours. Walking in, using it and walking out is the kind of thing that gets noticed and remembered.
What a good bar looks like
Full of people who are clearly local and clearly in a hurry. A price list on the wall rather than a menu in four languages. Pastries that are visibly running out by ten in the morning, because that is what fresh looks like at the end of a morning.
You are not looking for charm. You are looking for turnover.