Any legitimate firearms training course whether civilian, law enforcement or military, starts with a safety briefing.
The vast majority of accidental or negligent discharges can be completely avoided if the following rules are strictly adhered to at all times:
1) ALWAYS treat every firearm as if it were a loaded firearm.
2) ALWAYS keep the firearm's muzzle pointed in a safe direction such that if there were to be an accidental discharge, no person would suffer crippling injury or worse, death.
3) ALWAYS keep your finger off the trigger and out of the trigger guard until you are ready to take your shot on target.
4) ALWAYS be aware of your target and what is beyond it.
Reference "must read" linked documents below: