If we're talking about partial suspension hanging, then the trick is to block (only) the arteries on the right side of the neck that deliver blood to brains. You do it right, you lose conciousnes in under 10 seconds.
Only worry I have about this method is, that you will trash about even after losing conciousness. Worse case scenario is you manage to free the pressure after you've already suffered brain damage.
detailed information available at:
http://hightechchat.reocities.com/SoHo/opening/3630/part2/chap23.html