Meals generally include three courses, a drink, and coffee. Many restaurants have an ementa turistica (tourist menu), a set-price meal, most often served at lunchtime. Note that you'll be charged a couple of euros if you eat any of the couvert (or coberto) items -- typically appetizers such as bread and butter, olives, and the like -- that are brought to your table without being ordered.
Lisbon's restaurants usually serve lunch from noon or 12:30 until 3 and dinner from 7:30 until 11; many establishments are closed Sunday or Monday. Inexpensive restaurants typically don't accept reservations. In the traditional cervejarias (beer hall-restaurants), which frequently have huge dining rooms, you'll probably have to wait for a table, but usually not more than 10 minutes. In the Bairro Alto, many of the reasonably priced tascas (taverns) are on the small side: if you can't grab a table, you're probably better off moving on to the next place. Throughout Lisbon, dress for meals is usually casual, but exceptions are noted below.