Make a character write a letter. Not an email. Not a text message. An actual letter. 

Who’s this letter to? Does the letter explain your character’s relationship to its recipient? Does the reader already know the recipient? Or have you used this opportunity to introduce a new character?

What does the letter say? Do you, as the writer, include the letter in full? In snippets? Or do you simply paraphrase what your character is writing and thinking?

Some ideas: 

• Your protagonist could write a letter to you, the author. What would they say to you? Would they be grateful, or would they have a few bones to pick?;
• Your protagonist could write to another character or the antagonist;
• Your antagonist could write you a letter, or write to the protagonist or another character, and so on;
• The recipient of the letter could also write back.

Make sure that this letter offers your readers something new, what is it that we’re learning? Everything has to happen for a reason in your story, is this purely to show a character trait? Is it a clue as to what happens later? Is it to put new pressure on the relationship between your characters? 

Whatever motivates the letter, make sure you are discovering something deeper about the character or characters involved. 

Happy writing! 

Via: https://writersedit.com/254/resources-for-writers/weekly-writing-prompt-4/