Bread is served with all Italian meals and is part of the pane e coperto charge. Butter is seldom served except with breakfast. The container of olive oil on the table is for more than sprinkling on your salad. A plain broiled or grilled fish is enhanced with a few drops of olio, and maybe some lemon. In Venice, extend this to Monday, since the Rialto Fish market is closed that day as well.
Coffee is served after a meal, never with it.
Most places do not require men to wear a tie, but Italians do dress with casual elegance when they eat out, and they do not consider athletic shoes of any type to be acceptable with street clothes. Taking children to restaurants in Italy is not the problem it can be in France. Solo diners may be relegated to poor table locations. To avoid this as much as possible, reserve a table for two. Upon arrival, say your dining companion had to cancel at the last minute, and tell the waiter how sad this makes you.