Principles of Design
One goal of the artist or designer is to achieve unity in concept, form and purpose. Because unity of purpose can be perceived in psychological as well as physical modes, it must be kept in mind that the artist will vary compositions, making some appear visually stable and others unstable, depending on the concept and psychological effect that he or she wishes to achieve.
It is important to subjectify visual factors - that is, alter them according to personal feelings and intent. Some principles of visual organization (ways in which the Elements of Design are utilized) include the links below. If you follow them, you will see Art 2 examples of photo montage which illustrate each principle: