You will need:
1. Place a straight stick straight upright in the ground so that you can see its shadow.
The taller the object is, the easier it will be to see the movement of its shadow.
The narrower the tip of the object is, the more accurate the reading will be.
Make sure the shadow is cast on a level, brush-free spot.
2. Take your first reading in the morning, at least an hour before midday. Mark the tip of the shadow with a small object, such as a pebble, or a distinct scratch in the ground.
Try to make the mark as small as possible so as to pinpoint the shadow's tip.
3. Use a length of string exactly the same length as the first shadow you record.
Keep checking shadow's length every 10-20 minutes. You will find that the shadow will continue to shrink as the time approaches midday, when shadows are at their shortest.
4. The shadow will begin to lengthen after midday. When the shadow grows to exactly the same length as your string from the first measurement, mark the spot.
5. Draw a straight line connecting the first and second marks as above. This is your east-west line.
6. If you stand with the first mark on your left and the second on your right, you will be facing in the approximate direction of true north.
7. For an exact reading, your two marks need to be made at exact intervals before and after noon where you are, which means when the sun is at its highest point in the sky.