The sun rises in the east and sets in the west. At midday the sun will be due south. If you observe the suns movements you can get an idea of the cardinal points.
But what if you don't have all day and you want to find North/South now?
You will need:
1. A wrist watch.
2. The Sun.
Step 1: Aline Your Watch
Move your watch around until the hour hand is pointing at the sun (As its difficult to take photos facing the sun, I put a nail in a piece of wood and use the shadow to indicate the position of the sun).
Step 2: Imagine Lines
Imagine a line traveling through the 12 O'clock (green line) and another line pointing towards the sun (red line). Divide the angle that is made in half and this point will indicate Due South (yellow line).
Before noon you measure the angle created between the hour hand to the 12 O’clock, in a clockwise direction. After noon you measure the angle between the hour hand and 12 O’clock in an anticlockwise direction.
We will use the example of 7 O’clock:
At 7 am, we make an angle from the hour hand to 12 in a clockwise direction (7,8,9,10,11,12). This gives us a 150 degree angle, so South is at 75 degrees, half way between 9 and 10.
At 7 pm, we make an angle from the hour hand to 12 in a anticlockwise direction (7,6,5,4,3,2,1,12). This gives us a 210 degree angle, so South is at 105 degrees, half way between 3 and 4.
I hope this clears it up for you, but the best way to understand this is to go outside and try it out for yourself at differenttimes of the day.