Meta Principles
The strays
Form & Volume
Masses in 3D Space
Make shapes real looking by adding modeling (shading) and shadows.
Negative Space
Everywhere the object isn't
The empty space between the shapes defines the shapes. (Gestalt, Notan)
Economy
Your mental eraser
You are allowed to leave things out if they don't help the design.
Point of Focus
That thing right there.
The point your eyes are led to in a design.