This is a basic example. The horizon runs on the bottom line and the tree on the island runs up the line on the right. The sun also runs along a line. Because the tree intersects with the lines it makes it a 'power point' (No, not a PowerPoint).
The Dark Knight:
In the first image I have sectioned it shows how the lines contain what the main focus can be. The Joker is encased in the lines, smack in the center of the screen. I think this scene is very vertical in the bars. I have also noticed that the bottom line goes across his arms while the top line goes across his forehead.Ghostbusters:
This image is similar as it doesn't have a power point. The screen is divided between the three characters and it shows in the lines and intersections. Peter has the left most of the screen, Egon has the middle (more specifically the center box) and Ray the right most. Twice in this scene the lines intersect the bodies of the characters. The two vertical lines are between the arms and bodies of Ray and Peter. The elbow joints are also very close to the intersections.