How does a window manager register itself with the X Server?

Question

I was wondering how the window manager registers itself with the X server, and how it knows what process to kill when it goes about replacing the current window manager

Answer 1

X just keep waiting for the return of the process of wm/de. Suppose you have a line of exec awesome in your ~/.xinitrc. X will start and execute that line and monitor that process return. Try putting commands below of exec line, they'll never be parsed.