According to Andrew Loomis, in any succesful drawing, attention must be given to five P's and five C's1) as he calls them.
Five P's
Proportion, the three dimensions
Placement, a position in space
Perspective, relationship of viewpoint to subject
Planes, surface appearance as defined by light and shadow
Pattern, the deliberate arrangement of the tones on the subject
Five C's
Conception, a rough indication of an idea
Construction, an attempt to establish the forms from life or from basic knowledge
Contour, the limits of forms in space, according to viewpoint
Character, the specific qualities of individual units of your subject in light
Consistency, all the essentials of construction, lighting, and pattern, organized as a unit