Using a Letter in Narrative

QUESTION:  In my story, important information is revealed by a character reading a letter.  What is the most suitable way to write it?

I’ve written this kind of scene a number of ways.  

When the letter is being viewed by the viewpoint character and isn't terribly long, I've put the text in its entirety on the page but separated it from the regular text by having an extra space break above and below the letter and an inch-wide margins on both sides.  (The inch is from your normal margin, not from the paper’s edge.)  Some writers put this text in italics.

This method works particularly well when the content isn't highly emotional for the character.  It also works when the character is alone.

For longer letters, particularly those with emotionally charged content, I have a character read it aloud as dialogue to another character.  At certain important points where the character or characters are emotionally affected or the content changes things in a big way, I'll have the reading character stop and express an opinion, feelings, or questions.  A bit of dialogue/discussion between or among the characters will also break up a long monologue to make it easier for the reader to keep up and not be bored with too much information.  

When the character begins reading again, I say something like "Adam continued reading," or "Adam picked the letter up again and continued."

Normally, when a character quotes someone else, you use single quotes to denote it.

“Gramps always said, ‘You reap what you sow. boy.’”

If a character is quoting a letter, and the reader knows he is quoting it, you need only use standard double quotes.