Bed direction relates to Five Elements: East belongs to wood, beneficial for liver and gallbladder; South belongs to fire, beneficial for cardiovascular; West belongs to metal, beneficial for lungs and large intestine; North belongs to water, beneficial for kidneys and bladder.
Choose direction based on Bazi preferences: those who like wood should face east, those who like fire should face south, those who like metal should face west, those who like water should face north.
If unsure of preferences, can choose facing east or southeast—these are gentler directions suitable for most people.