John comes out, clutching the book. Suddenly he bolts from the porch, running to his house next door. That's it in a nutshell. There are variances available at moments in the script but the beginning writer should probably stick to the master scene approach. Your job is to tell the story as directly as possible, NOT to direct the movie.
Page numbers go in the upper right corner, followed by a period.
A slug line tells the reader where we are, what we are looking at. Slug lines are in caps, followed by a double space to the next unit, which usually is an action line. An action line describes who is in the scene and what is happening. Beginning writers overwrite action lines. Often, in the action line, a character name is in caps the first time it is mentioned, not in caps thereafter.