White Dove: "Do people know just when they are about to take their last breaths?"
If it is a lingering debilitating death, I think they do know, just before the end.
My grandmother asked to be wheeled through the great hallway so she could look at everyone's portraits. She stopped and looked at each one and had some comment to make about a special memory of them.
She died a couple of days later.
If it is a sudden death, like what happened to me...I did not think of dying at all. There were things happening and I was caught up in the strange physical sensations and then wondering why people could not hear me when I answered. I was just coming to realize that I had separated from my physical self.