There are only two causes of the accidental discharge of a firearm. A lack of knowledge and carelessness are the only two causes of an accidental firearm discharge.
There are three rules of safe gun handling. Learn them right here. Repeat them as many times as you need to:
1)-ALWAYS point the barrel of the gun in a safe direction. A safe direction is defined as a direction where if the gun discharged, nobody would get hurt. The best direction to point a gun is generally at the ground and to the side.
This is known as the Golden Rule Of Gun Safety.
If everyone followed this one rule, it would bring an end to accidental firearm related deaths.
Be aware that the "safe direction" may change as you change your location.
2)-ALWAYS keep your finger off the trigger until you are ready to fire. There is a natural tendency to place the index finger inside the trigger guard. This MUST be avoided. Condition yourself to place your shooting hand index finger along the side of the frame.
If you stumble and begin to fall while holding a firearm, please be aware that your hand and fingers will begin to clench naturally during your fall. That is why you must condition yourself to place your trigger finger outside of the trigger guard when handling or carrying a gun.
There is no reason whatsoever that your finger should be on the trigger unless you have safely and appropriately acquired your target and your sight picture and are ready for the trigger squeeze.
3)-ALWAYS Keep the action open and the gun unloaded until you are ready to use it. The action is the moving parts of the gun that allow loading, unloading, firing and extraction of the empty case or shell. If you are not ready to use it, keep the action open and unloaded.
With an open and unloaded action, the only injury that might occur, is if you drop the firearm on your foot.