If it's a feeding response, and you've got an ambitious feeder attached to you... hold as still as possible. Let your arm/hand go limp - if you twitch even slightly, you'll get coiled harder. I had one that got my thumb as I was moving a hut out of the way, and didn't even think that I smelled like rats from the other snakes... as soon as I let me hand go completely limp, snake let go and started looking for the head.
As far as quickest and one of the safest means of removing a snake (especially if it's a big one), have an ice pack or ice cubes handy. I've used cool water and even room temperature water poured over the face/into the mouth with luck... but I've also had a snake be completely submerged with no luck... ice cubes/ice packs put up to the snakes nose/heat pits if they have them works like a charm. Don't even necessarily need to touch the snake.... they feel that extreme cold and instantly release.