How to Write a Condolence Letter
newyorker.com
newyorker.com
I think it's worth avoiding pre-printed cards. If you know the bereaved or the dead person well enough to want to express your condolences, then write a letter or note. It doesn't have to be more than a few sentences, unless you want to write more. Yes its a hard thing to do, but it's also necessary. And in my experience it can help the writer too.