The medicine wheel normally follows a cycle of birth to death of ideas, normally entering in the east and going round to the north. In the East the sun rises, so this direction is often related to the birth of ideas and far sightedness and is often symbolised by the eagle. In the South this is the direction of innocence, and is often symbolised by the coyote, as this is the animal that tricks us back into childhood. In the West the bear energy links us with our dreams and the void of all creation. In the North the buffalo energy represents spirituality and wisdom.
As you look at ancient beliefs though, it is stunning the similarities, with so many traditions having four compass directions in their teachings. I mean, I have never seen a system with 5 directions or 3 directions! So really in many ways the compass represents balance (as all the directions of the compass make up all of who we are) and the bringing together of all these diverse aspects to make something beautiful.