Know the rules before you break them!
Design is informational
Though form and function does not necessarily improve the content of your message it can improve the ease with which it is accessed--and design can effect how well it is understood.
Design is a visual language
Use icons as prompts - On paper, scissors mean to cut something out, a clock means time-sensitivity, a knife and fork means food, and so on. Think of innovative ways to spare words and prompt action with illustrations.
Design makes a statement
Make it informational - A book typically contains editorial information--to entertain or to educate--not to sell. You can do the same by mixing your selling message within the editorial coverage of your subject.
Design leads the viewers eye
Guide the reader - Use subheads and visuals to draw the reader through your booklet. Words and visual cues tell the reader where they are and help them focus on one subject at a time.
Use icons instead of words
People from any language can understand them. Plus, you don't need to read anymore, instead you lead the viewer's eye to what is important.
Design follows rules such as balance, contrast, dominance, harmony, rhythm and unity.
Be stylistically consistent - Try to stick to one illustration style throughout. Using images from different sources can degenerate into a patchwork. You can for example double your image - The small version of this illustration conveys the message it was designed to. The large version is a design element used to echo the idea and add interest to the page.
Things to keep in mind:
Everything on a page should align with something else
Repetition reminds the viewer
Use enough white space
When space is a premium, drop smaller and less important graphics
When in doubt, don’t use it
Don’t let graphics distract from the message
Use few fonts (preferrably no more than two different fonts on one page)