When photographing a subject, it's tempting to center things in the middle of the frame. This is sometimes effective, but you can introduce more emotion and visual impact by placing the subject in the upper, lower, left, or right third of the frame. In the examples below, notice how a subtle difference in subject placement can drastically affect the overall mood of the image. This works with living people and creatures as well as landscapes.
(https://www.nyip.edu/images/cms/photo-articles/change-the-mood-with-the-rule-of-thirds-1.jpg)
EX1: In this image of the Iguana, the subject itself is rather centered in the frame, but the reptile's head has been placed in the upper third. This minimizes any unnecessary space above the creature.
(https://www.nyip.edu/images/cms/photo-articles/change-the-mood-with-the-rule-of-thirds-2.jpg)
EX2: If you have a very interesting sky, you may want to show more of it, placing the horizon line in the bottom third of the frame.
(https://www.nyip.edu/images/cms/photo-articles/change-the-mood-with-the-rule-of-thirds-3.jpg)
(https://www.nyip.edu/images/cms/photo-articles/change-the-mood-with-the-rule-of-thirds-4.jpg)