I have to throw my two cents into this conversation -- espcially coming from the country where you find books by Gabriel García Márquez filed under M.
First and middle names are
usually, note I say usually, the names that you are given at birth. For example, my parents chose to call me Andrea Susan. By family custom, some families use surnames as given names. I know a Martha Kent B____ and a Philip Glasgow C____.
Just to confuse things, some people go by their middle name and some people have more than one or two given names -- like George Herbert Walker Bush. George is the first name and Herbert Walker are middle names.
Last name, surname, is the family name, the one that you inherit from your parents. Most English speakers use just their father's surname but in the last 40 years we are seeing many changes to this because of both the feminist movement and the increasing Spanish-speaking population within English speaking borders.
Traditionally in the English speaking world, married women use just their husband's surname. A married woman's maiden name is her parent's surname.
Many married women use their maiden name as a middle name and stop using the middle name they were given at birth. For example: Andrea Susan Jones becomes Andrea Jones Smith -- Smith is her surname and Jones is her middle name.
In an alphabetical list, you will find her name under J for Jones--not S for Smith. That is why García Márquez ends up in M -- because the last name in the list is the surname. Square pegs never fit in round holes. But we are learning!
More recently, like in the last 40 years, however, many women have opted to keep their own family name after marriage. This becomes an issue when children are born. Do the children take one of the surnames? Do they use a hyphenated surname? These decisions are being made on a family by family basis. The first generation of hyphenated surnames is just starting to marry and we don't know what will happen when Mary Jane Lautenberg-Guttenham marries Juan Carlos Hernández Rodrigues and they start having children.
So then, how to fill out those forms. My answer: first name and middle name are always given names or the given name-maiden name thing. Middle names can be left blank. Last name is looking for the surname, the family name or even names -- with or without a hyphen. Smith, Lautenberg-Guttenham or Hernández Rodrigues.
Andrea