When shooting within a 35mm rectangular frame, where do you place the subject within the frame for maximum effect?
The "Rule of Thirds" answers this question. As you shoot, imagine the frame divided by lines that create three equal columns and three equal rows. Where the lines intersect are optimum positions for subject placement. Of course, the lines themselves also prove useful as guidelines.
The reason that the "Rule of Thirds" works so well is that we tend to focus on a position one third from the edge of the frame.
With landscapes, placing the horizon line in the exact middle (50% point) can be confusing, since we must ask "is the sky dominant or is the earth dominant?". We solve this problem by placing the horizon along the lower third line when emphasizing the sky, and along the upper third line when emphasizing the earth.
If you have dramatic foreground elements close to the camera, place the horizon near the top of the picture.
While the "Rule of Thirds" is a quick method for improving your photos, it is so widely used that our photos may lack real appeal. Don't be afraid to break this rule. In fact, start with placement at the obvious intersection points and see if you can improve from there.
Leave space in front of moving objects so that they can "move" into that space. A motorcyclist, driving hard to our left, will appear to be leaving the picture if we place him on the left edge of the photo. In fact, he may appear to be going over a cliff. Instead, give the motorcyclist more room in the picture in which to "move" into.
Nose room involves giving a person room to breathe. That means there is enough area in the photo to prevent suffocation.