This is a rather splendid guide to writing a suicide note.
In general, use first person.
It creates a sense of intimacy and makes it easier for a reader to see things from your point of view, if you want to use a different viewpoint, be sure that you stick to it throughout your whole note.
Don’t reveal your methods.
This is most important when taking poisons and pills. Telling everyone what you took just makes it easier for them to give you the treatments needed to revive you. Alternately, you do not want someone to find the note that details which bridge you’re jumping off of before you get that chance to jump. They might be able to stop you. People will find out how you did it once the autopsy reports come in anyway.
but my favourite:
Make sure it’s not too long.
There is a reason it’s called a suicide note and not a novel. Try to keep it around two or three pages at the most. Avoid the temptation to mention or leave a little note to everyone you know. Not only does that get dull fast but you’re certain to leave someone out.
image is kurt cobain’s suicide note