Pictorial form of presentation does not have magical instructional effectiveness just because they are pictures.
Diagrams cannot act as stand-alone resources, as long as they are not self-explanatory.
They need to be seen as part of a wider instructional system.

Good design is fundamental to the success of a diagram.
To the design and development process contribute several experts:
- subject expert: specifies the content matter,
- instructional designer: implements the diagram into the learning process,
- artist: creates the diagram,
- media consultant: implements the diagram into the actual media environment.

The instructional designer needs to strike the difficult balance between simplifying the presentation and providing support.

To be effective a diagram must: