Left arm above the wrist joint with the watch face inward. Meaning the face is towards the body. It protects the face from hitting things and getting scratched but also since my watch is "very" luminous - don't want the enemy to see it at night. Or at least that was why some years ago - now its just habit. Plus when you are sitting in a long boring meeting its easier to read the watch without conspicuously turning your wrist over.