PROCESSING BEGINS BEFORE YOU PAY ATTENTION. Organizational structures, motion and contrast can affect the way a message is decoded. Good designers build in factors which are attended to involuntarily and automatically. Similarly, organization and structure help those who are already attending. 
Attention Anecdote: The fire alarm went off this morning. No one knew what the noise was, but the insistent wail could not be ignored. The siren went from ear piercing high, lowered, then screamed again. Bright lights flashed in the halls. Before anyone knew what was happening, their attention was captured.

        In the information processing model, four cognitive processes occur.

        Selection: attention to certain pieces of incoming information in sensory memory. Followed by a transfer to short-term memory for additional processing

        Organizing: the learner builds connections in short-term memory

        Integrating: transfer of information from long-term memory to short-term memory to connect with incoming data.

        Encoding: transfer from short-term memory to long-term memory

"A great deal of perceptual organization occurs preattentively,
not under cognitive control." 
If you want to notice it, change it.
Humans are very sensitive to change. Attention can be directed through carefully designed changes. Sudden changes have the greatest impact on attention. These changes can occur across the senses: change color, texture, size, placement, texture.
If you want it noticed, use a horizontal-vertical orientation.
There is a natural tendency for people to follow horizontal or vertical lines. Diagonal lines do not receive the same amount of attention. Readers tend to follow these lines according to the direction of their reading system. For example, readers of English, read from left to right and from top to bottom.
If you want it noticed, draw clear boundaries.
It should be easy to differentiate between objects in the foreground and those in the background. Keep boundaries strong, so that viewers can "see" different parts of your message. It should be easy to tell the difference between the main ideas and the details.
If you want it noticed, organize into meaningful parts.
Items which are in close proximity will be viewed as "units." A designer can direct the eye through appropriate grouping of items which go together. Organization imposed preattentively affects the way cognitive processes operate.

Once voluntary attention is given, the processing of information is already underway. Once conscious attention is paid, there is a change in the way information is processed. Pre-attentively, there was no direct communication with long-term memory. Now, both top-down and bottom-up processing occur simultaneously. Since processing has already begun, the designer can use the following.
Click on each box for examples.
guidelines. For graphic illustrations of these concepts, click on each box for examples or non-examples.
Avoid irrelevant information.
Draw attention by using contrast .
Avoid extremes- sounds should not be too high or too low, colors not too bright or too dull, textures not too smooth or rough.
Control order by using: lines, arrows, composition.
Cluster related pieces of information

You may be interested in locating more information by visiting the following sites within the Encylopedia of Educational Technology.