Location uses degrees. 0 degrees is East.
You can also script facing commands to force an NPC to reorient and face in a specific direction:
AssignCommand(oNPC, SetFacing(90.0));
You can also use fixed cardinal direction constants:
float DIRECTION_EAST = 0.0;
float DIRECTION_NORTH = 90.0;
float DIRECTION_WEST = 180.0;
float DIRECTION_SOUTH = 270.0;
Alternatively, you can face them towards another object:
AssignCommand(oNPC, SetFacingPoint(GetPosition(oObject)));
This can be temperamental though. Often they won't change their facing until they perform an animation, so adding a short anim to a script is something necessary if you are trying to assign facings in a conversation, especially with interjections from companions where the NPC may be changing their facing to look at multiple different speakers.