1. Find the North Star
A little astronomy goes a long way. Find the Big Dipper, which is one of the clearest constellations in the northern night sky; it looks rather like a ladle.
The two stars that make up the “pouring” side of the ladle line up to point directly at the bright North Star.
2. Moss on trees and rocks
The idea that moss tends to grow on the Pole-side of trees and rocks, away from the equator and therefore the sun, is a misnomer.
The idea probably started in a region where this was the case, but internationally, it doesn’t hold true.
Specific regions may have types of moss and lichen that do grow this selectively, but there’s too much variation to rely on this as a rule unless one intimately knows the flora and region in question.
3. Tracking the sun’s shadow
When the sun is approximately in the middle of the sky, plant a stick in the ground and mark the tip of the shadow. Wait half an hour or so and mark the tip again. A line between the two points is approximately east-west.
4. Using the crescent moon
When the moon is at its highest, draw an imaginary line through the tips of the crescent and trace it down to the horizon. That point lies approximately south of your position in the northern hemisphere, vise versa in the southern hemisphere.
5. Drier hillsides face north/south
Look for flora that appreciates drier microclimates, such as cacti. In the northern hemisphere, cacti and other dry-loving plants will be more numerous on the south facing slopes. Vise versa for the southern hemisphere.
6. The wristwatch method
This works on old time analogue wristwatches, not so much with digital ones. You can get round this by quickly drawing a clock face of the current time on a piece of paper and orientating it appropriately.
Hold the watch face flat and, in the northern hemisphere, point the hour hand at the sun. Bisect the angle between the hour hand and the 12 o’clock mark, and that’s your north-south line.
In the southern hemisphere, point the 12 o’clock mark at the sun, and bisect the angle with the hour hand.
7. Improvised compass
Magnetize a needle by stroking it extensively (in one direction only) on natural fibers, put it on a floating leaf or piece of wood on still water and it should orientate north-south.