In essence as photographer you must separate image subject from the overall image and the context in which the subject is put or found (object/background).
The following is just a guidline to achiving this, and also for ensuring useful and commercially viable visuals.
Subject - Background Relationship
Vision is a scanning procedure the eye and mind look to separate the perceived subject from the background, this is dependant on the interests of the viewer. The background becomes an integral part of the image aiding the process of directing the viewers attention away from objects or background, to the subject.
A viewer searches for meaning or recognition within the visual frame.
The aim of the photographer is to direct that process as successfully as possible.
An unmoving picture, framed, allows for continual scrutiny. Remember we are rendering a three dimensional scene into a two dimensional frame.
A clear meaning is always more useful to graphic designer needing to convey a specific message or feel to a design.
The perceptual grouping of visual elements is aided when these elements are grouped, placed close to one another. Changing the spatial relationship of objects by taking a three dimensional scene with; height width and depth and reproducing it into a two dimensional frame with only height and width presents a challenge. Close objects are attracted to each other by the viewers perceptual grouping, distant objects repel one another.
Ambiguity creates subject confusion in the subject/background relationship.
Careful positioning of subjects within the frame and relative to the background can create dynamism to an ordinary image.
Commercial images need negative space that designers can use as a background, or as a lead in or lead out of the image and or frame.
Objects similar in size shape, position, colour, meaning and tonality can form a repetitive pattern.
Patterns occur in the mind because of a tendency to group similar things. This can be used photographically to aid in the subject/background relationship. A break in pattern stimulates interest and we notice the difference immediately. A group of green apples with a red one placed in the middle for example.
Symbolic association, creating images in the viewers mind, the viewer becomes pro-active in creating an image which has greater meaning. An example; combining a roadside memorial cross and a speeding car in the background thus symbolizing the carnage on roads.
These are three usefull aspects to add to your checklist before pressing that shutter, happy shooting!