if nothing else, write it on a piece of paper, sign it, date it, and put it in a safety deposit box!
In some states a handwritten will is acceptable. In my state, however, they are not recognized. Because I want a basic presumption toward life in my living will, I have to draft the thing from scratch. Unfortunately, most living wills are geared toward death.
I know this may sound GOOFY (no one laugh), but there is an addendum to my living will saying if I'm ever comatose, read to me...play Gene Kelly movies, play Mozart on CD, but give my brain something to "chew" on!