Which is the most important training required for warehouse labors to avoid mishandling the equipment's ?

Required to train them under a senior responsible staff on how to handle, maintain and safety.

licenced equipments should be handling by staff with required permits. 

Actually there must be trained team leaders who would be the responsible for save and smooth loading, off-loading and stacking properly to avoid any mishandling. Every equipment may have vary staking requirement therefore, team leader must be well aware and responsible for any transaction, then relevant supervisor would be response to take care about all matters.

Restrict unauthorized access to the equipment will avoid mishandling errors