As a matter of interest, I have been handed a loaded gun on three occassions that was thought to be empty. Once it was a Reising SMG, which I fortunately knew how to clear.
One of the first things I learned was how to clear many types of firearms. This has stood me in good stead over the years.
I hand it to them action open.
If someone hands me one , the first thing I do is take the magazine out ( if it has one ) , then open the action and physically look in the chamber.
When handing someone me gun I remove the magazine and open the action to eject the chambered round. I then drop the hammer, method depending on which of me guns it is.