What scenes from the film summed up the theme most effectively? How did the lighting, setting, camera shots and acting contribute to the theme in those scenes?

This really depends what theme you are referring to, there are many. The theme of intimacy between students and teachers is best scene during the montage of Mr. Keating on the soccer field with the kids. With the song Ode to Joy, the boys all pick up their much-loved teacher under a crisp orange sunset of a fall evening in Vermont. The reds and oranges with fall colors are splendid !