In this posting I can’t make available any of the examples to you – for those you’ll have to buy the book; but I can share the rules. Here they are, with commentary extracted verbatim from Timothy’s explanations:

1. Have a concept: It doesn’t matter how amazing the thing is to look at,without a clear message.
2. Communicate – don’t decorate: Form carries meaning, no matter how simple or abstract, and form that’s not right for a given message will communicate messages that you don’t intend.
3. Speak with one visual voice: Make all parts talk to each other – in the same language.
4. Use two typeface families maximum.OK,maybe three: Choose typefaces for specific purposes. In doing that you’ll need to define what the purposes are, and you’re likely to find that there are only two or three.
5. Use the one-two punch! Focus viewers’ attention on one important thing first, and then lead them through the rest.
6. Pick colours with purpose: Don’t just grab some colours out of the air.
7. If you can do it with less, then do it: The more stuff jammed into a given space, the harder it is for the average bear to see what they’re supposed to be seeing.
8. Negative space is magical – create it, don’t just fill it up: Space calls attention to content, separates it from unrelated content around it, and gives the eye a resting place.
9. Treat the type as image, as though it’s just as important: Type is visual material that needs to relate compositionally to everything else included in the design.
10. Type is only type when it’s friendly;  Make it legible, readable or whatever you want to call it. [At this point I should explain that I could barely read the type in the book with spectacles on and an overhead light. Obviously there is readability and readability.]
11. Be universal – remember that it’s not about you: Talking to yourself is the domain of the fine artist. Being universal is the domain of the designer.
12. Squish and separate: Create contrasts in density and rhythm by pulling some material close together and pushing other material further apart.
13. Distribute light and dark like firecrackers and the rising sun: Above all, make distinctions between light and dark noticeable and clear.
14. Be decisive. Do it on purpose  – or don’t do it at all. A great deal of the process of understanding visual material is the ability to distinguish the difference between things. Decisiveness makes a viewer more likely to believe that the message means what it says.
15. Measure with your eyes – design is visual: The eyes are funny things; they’re often fooled by visual stimuli.
16. Create images – don’t scavenge: Nothing is more banal or meaningless than a commonly-used instance of stock photography that shows up everywhere.
17. Ignore fashion – seriously: Style the project around the meaning, not the audience’s expectations of current stylistic  conceits.
18. Move it! Static equals dull: If a layout is clearly flat and fails to offer a sense of movement or spatial interaction, the viewer’s brain is likely to be disinterested.
19. Look to history but don’t repeat it: To slavishly reproduce a particular period style because it’s  really cool is just unacceptable.
20. Symmetry is the ultimate evil: Symmetry shouts very loudly that the designer is lazy and likes to let the format do the designing.

It’s possible that the graphic designers that you work with will simply refuse to abide by any rules. Fair enough, but do remind them that  "rules can be broken – but never ignored" (David Jury, typographer and author, 2004).

Source: Clive Shepherd