First Name or Title?
Brazilians are as informal as they are hierarchical. For example, first names are used frequently but titles are observed.
In formal situations, for superiors, use titles like Mr. and Mrs. followed by their surnames. In informal situations persons always use their first name. The terms “Seu” (for men) and “Dona” (for women) are used with a certain regularity. Doctors and lawyers are always called Doctor.