Even if there is just one subject to be placed, there is one fundamental choice to be made, "how much of it do we want to see?" This depends on three considerations:
Content of the subject
Is it unusual enough, detailed enough, that we want to see more of it? Think of rare animals or fine works of art.
Relationship with environment
Is the setting of the subject important? Think about the context of the activity taking place and its scale.
Intended impact on the viewer
What do you want the viewer to feel? Strong presences like explosiveness and awe? Or subtler feelings of calmness and curiosity?