I thought a lot about this subject throughout the years and have come to the conclusion that the only way to do it properly is gun to head.  All other ways have unacceptable failure modes.  It's not good to fail at this.  Failing means making the situation on this planet far far worse.  I still have my brain, I still have my skills, I still can do something, I still have hope.  Being in a vegetative or paralyzed state, I have no hope and little chance of doing it again.  It has to be a gun to the head.

I suppose I could expand upon this and write a book on the subject.  How to commit suicide would be one fucked up book -- which means someone probably already wrote something like that since I'm far from the only person on this planet who have or had these same thoughts.  There probably are lots and lots of people like me.