To use a watch bezel as a compass, hold the watch faceup in the palm of the hand and parallel to the ground. Turn to point the hour hand at the sun. The line halfway between the hour hand and 12 o'clock is south.
This technique only works with an analog watch and only during daylight hours. In the Southern Hemisphere, this technique locates north. The same thing can be accomplished by drawing an analog watch face on a piece of paper and marking the hour hand on it using the correct time from a digital watch.
This technique works even on overcast days as long as there is enough sun to cast a shadow. It is more accurate farther away from the equator because the sun's shadow is longer.