The principles are similar to what we teach in NRA Basic Pistol, and review in subsequent tactical couses.
Here's the webpage with fancy graphics...
https://gunsafetyrules.nra.org/
Note that this applies to everyone: Civilian, Military, Police, Private Guard, your aunt Martha...
It's pretty basic, but you just gotta do them EVERY SINGLE TIME you handle a firearm.
That and when storing a firearm, never store it loaded. If you have a gun for home defense, it's kept loaded and is not being "stored" - and that firearm should have it's access somehow controlled. I use pushbutton safes for home emergency defense handguns.
In training, we check students as they walk into the building, and show each other that firearms are unloaded every single time we handle them in class. Simunition training requires special protocols, especially because you're intentionally pointing firearms at targets that might be people.