The clapper loader (or 2nd AC) is generally responsible for the maintenance and operation of the clapperboard, while the script supervisor is responsible for determining which system will be used and what numbers a given take should have. While these are usually fairly obvious once a system has been agreed upon, the script supervisor is usually considered the final arbiter in the event of an unclear situation.
Sometimes a "tail slate" or end slate is filmed at the end of a take, during which the clapperboard is held upside-down. This is done when the slate was not captured at the start of the take due to the camera being set up for the shot in such a way that the board cannot be captured, for example when a specific focus or frame is set up and cannot be altered until the take is complete. Tail slates are also commonly used when the director makes the decision that clapping a slate at the beginning of the scene would be distracting to the actor, such as when filming a highly emotional performance.
"A point of view shot (also known as POV shot, first-person shot or a subjective camera) is a short film scene that shows what a character (the subject) is looking at (represented through the camera). It is usually established by being positioned between a shot of a character looking at something, and a shot showing the character's reaction (see shot reverse shot). The technique of POV is one of the foundations of film editing." wikipedia
Point-of-view, or simply p.o.v., camera angles record the scene from a particular player's viewpoint. The point-of-view is an objective angle, but since it falls between the objective and subjective angle, it should be placed in a separate category and given special consideration. A point-of-view shot is as close as an objective shot can approach a subjective shot—and still remain objective. The camera is positioned at the side of a subjective player—whose viewpoint is being depicted—so that the audience is given the impression they are standing cheek-to-cheek with the off-screen player. The viewer does not see the event through the player's eyes, as in a subjective shot in which the camera trades places with the screen player. He sees the event from the player's viewpoint, as if standing alongside him. Thus, the camera angle remains objective, since it is an unseen observer not involved in the action."
—Joseph V. Mascelli, The Five C's of Cinematography[1]