It is difficult to answer in a specific way because all depends on the content of the letter or purpose and who the letter is address to , like a family member, friend and so on. But to answer that would be, " Tu amigo, ________ . Meaning " Your friend_______.
The 3-letter name of a Spanish gentleman is "Don." It is traditionally used as an honorific title before a man's first name.
Hidalgo - traditional Spanish nobility title for male person.
the appropriate thing is a comma
You could say "mejor amigo/a".
You use commas between items in a list, between the date and the year, and after the greeting in a friendly letter.
Private gentleman has written: 'A letter from a private gentleman to an English peer'
A friendly letter is a letter to a friend
A friendly letter is a letter to a friend
Gentleman in the city. has written: 'An account of the Scotch plot, in a letter, from a gentleman in the city, to his friend in the country'
gent
A comma is placed after the greeting in a friendly letter.
gent