Many people get caught up writing sympathy notes, thinking they need to say something profound and not coming up with anything. This often results in procrastination, which leads to not sending a sympathy note at all, which is one of the worst things you can do. 

Amy Cunningham, who also directs funerals at our favorite end-of-life education venue, Green-Wood Cemetery, recently hosted a workshop on writing condolence letters. She held out one of Ernest Hemingway's letters as a good example:

"This is not a good letter, Charlie, but I feel too sad to write a good one." 

"Aiming for excellence is only going to hold you up," said Cunningham.

Here is a list of do's and don'ts that we gleaned from Cunningham's advice:

Do
Send an acknowledgement to the bereaved.
Keep stationery, cards, and stamps on-hand to thwart procrastination. 
Use the word "death" rather than "passing," "died" rather than "passed away."

DON'T
Think that nobody will notice you didn't send a note. They will.
Include platitudes that could be offensive, for example "I know how you feel," or "This is God's plan."
Overthink the message. It's more about the gesture than what you write. 

Source: The New Yorker