In the Southern Hemisphere, you can't see the Big Dipper [source: National Geographic Education]. Not that it would matter if you could, because you can't see the North Star, either. Were there a corresponding Southern Star, navigating below the equator would be as easy as navigating above it. But alas.
To find south, look for the Southern Cross constellation, also called the Crux. The Crux, along with two nearby stars, will reveal the general vicinity of true south.
The Southern Cross is a group of five stars in the Milky Way that, with its "dots" connected, takes the form of Christian cross. The way to distinguish the Cross from other star groups is by its pointer stars – the brightest stars in the nearby constellation Centaurus. If you spot a possible Cross, scan its immediate surroundings for two very bright stars. An imaginary line connecting the pointer stars to the Southern Cross will intersect the Cross's top star.
Once you've got the Cross, with an imaginary line forming its upright, erase the imaginary line through the pointers and draw a different one, this time running between the pointers at a 90-degree angle to each. Keep drawing until it intersects the line you've drawn through (and beyond) the upright. That point of intersection is a good estimation of the location in the sky above the South Pole, or true south [source: Wilderness Survival Skills].
Direction is a key factor in navigation, but locating the stars above true north and south serves another purpose, as well – an arguably more important one for the truly, completely lost. For this one, though, regardless of hemisphere, you haven't got all night.