Rule One: All guns are always loaded.
If you watch regular shooters they will always check that a weapon is clear before handling it even if the person handing it to them just cleared it. You can NEVER be too careful.
Rule Two: Never let the muzzle cover anything that you are not willing to destroy.
Guns are very useful. Guns can be fun to shoot. They kill. Keep your weapon pointed away from people at all times.
Rule Three: Keep your finger off the trigger until your sights are on the target.
Your brain is your best safety. No finger on the trigger gun no go boom.