Besides looking at the rule-of-thirds for photo composition, you can use the four key point intersection of the vertical and horizontal of the imaginary lines for the placement of subjects. The four key points create interesting eye catching subject in photography.

By placing the subject on the one of the points, it creates an imbalance in the photo composition. Though the photograph is interesting, it creates a bit of a tension. You may of course look for a secondary object or feature to counter-balance the picture composition by placing it on the opposite diagonal point. The picture will create two points to make the eye go to and fro between the primary and secondary subject in the photo composition.