A user notifies you that the monitor on his notebook computer is not displaying anything. what should you do first?

I would plug up the computer and see if the battery is dead. If it is then that was the problem, but, if the battery wasn't dead then I would tap the monitor on the back and see if it blinks or displays something, then I would conclude that it is a bad connection to the monitor inside the computer and that I would get it checked out and fixed.