Hello friends,30 degree rule is just another rule like 180 Degree Rule, 180 degree rule tells that all cameras should be kept only on one side of the subject in a multiple set up, where as 30 degree rule tells that there should be at least 30 degree of change in camera angle while shooting sequence shots on a single person or subject continuously, this rule is mostly applicable for television format rather than films. But this is a very basic rule followed by every film maker world wide but the consideration of the change in the angle differs from person to person i.e this rule says that there should be change in the camera angle for about 30 degrees while shooting a sequential shots but most of the directors prefer 10-15 degrees of change in the angle rather than 30 degree.
This rule is helpful in overcoming jump cuts that may occur if same kind of shot is being repeated again and again. And this rule is a very fundamental rule in film editing.