Question: how to train puppies not to fight each other?
Answer: Natural Interaction. Put the dogs together. ... 
Monitoring. Observe the puppies at play. ... 
Spot the Signs. Note down the gestures that precede fighting. ... 
Learn the Causes. Note down the stimuli that provoke fighting between your puppies. ... 
Divert Attention. ... 
Positive Reinforcement. ... 
Repetition.