If your lost in the wilderness. Knowing which direction you're heading can be very important. For instance you may know the park you're in is a certain direction from a town.
This method of finding North depends one the knowledge that the sun rises on the east and sets on the west. There are many ways to find north but this is just one of the simplest ones.
You'll need something that stands upright and casts a shadow. It also has to be sturdy so it won't sway in the wind. The simplest thing is to just find a straight stick and push it into the ground.
You'll need the flattest surface you can find. Dirt works best but if you have to do it over grass. Just find the flattest spot you can find.
Mark the very tip of the shadow with a rock or anything you can find. This starting point is your "west" mark.
When you mark the tip of the shadow try to mark the very tip. This stone has a sort of arrow shape so I put the point right at the end of the shadow.
Wait about 15 to 20 minutes. The shadow line will move to one direction (depending on if you're in the norther or Southern Hemisphere). Then mark the tip of the shadow again with another rock.
Now imagine a straight line between the two stones. Or lay a straight stick between them. This line runs from west (first marker) to east (second marker). Now you can calculate which way is north.
Keep in mind that this method finds solar north which will be a little off from the magnetic north you'd find with a compass. But it'll still give you the general direction to head to safety.