All successful design employs good conceptual ideas, the result of a thorough brief. It's in the application of these ideas that the design really takes shape. During this time the designer has a set of guidelines in their toolkit which they consciously use to build their design.
THE 5 DESIGN PRINCIPLES:
Alignment creates a sharper, more unified design.
Repetition unifies and strengthens a design by tying together otherwise separate parts.
Contrast is the most effective way to emphasise and generate impact with a design.
Hierarchy creates organisation and direction.
Balance provides stability and structure to a design.
A good designer can tell you which principles they use in their design. Shillington College teaches design principles from the introduction stage through to complex, multi-layered Photoshop documents using photographic images, graphics and type.
