E-learning Design Principles
Ruth Colvin Clark and & Richard E. Mayer, explain in their book The Science of E-learning, that Cognitive Learning Theory includes both the process for learners to actively make sense of the contents and for teachers to attempt make the learner process appropriate for the learner. To create e-learning instruction that really works, Clark and Mayer suggest instructional designers use six e-learning principles in mind when developing e-learning that really rocks, i.e. works well, fosters cognitive learning, and maximizes the learning outcome. The principles are listed below.
Multimedia Principle
The multimedia principle states that words and graphics should be used together instead of alone. Pictures help learners understand and make sense of the material. Pictures should, however, be relevant for the learning, i.e. not be there just for decoration.
Contiguity Principle
To make sense of the presented materials, corresponding graphic and words should be placed next to one another.
The below picture has been enhanced with arrows to further specify how the words relate to the graphic. It is a good example of the use of the contiguity principle.

Modality Principle
The modality principle suggests that we present audio narration instead of onscreen text. This is because humans have two input channels: visual and auditory channels. Using verbal words together with graphics we avoid visual input 'overload' through one channel.
Click the image below and consider how audio can can enchance the presented image.
Redundancy Principle
Avoid redundant onscreen text together with onscreen graphics. When you present words in both text and audio narration you may hurt learning because students miss the visual.
The picture below is an example. Click it and consider the redundancy.
Coherence Principle
Including interesting but unrelated material can hurt learning. Extra stuff - Clark and Mayer humoristically call it "seductive materials to spice things up" - will interfer with the process of making sense of the material. Extra background sound, extra visuals, and extra words should therefore be avoided.
This YouTube video is an example of how extra is too much. The material is presented with sign-language (gestures), audio, captions, and with background music:
Personalization Principle
The personalization principle states that we should use conversational style and virtual coaches. Research, according to Clark and Mayer, research has shown that students work harder and learn better if they have a coach that speaks to them in an informal human voice. Avoid formal language and/or a synthetic voice.
Suggested Reading
' E-Learning and the Science of Instruction' by Ruth Colvin Clark and Richard E. Mayer. John Wiley & Son, Inc. Pfeiffer 2002. ISBN 0-7879-6051-9.