Putting all the following rules together might give us a set of margins such as those shown in the image at the top of the sidebar.
Not All the Same
Avoid using the same margins on all sides of a publication. In facing-page documents, the inside margin should be smaller than the outside margins. The bottom margin is usually larger than any other margins.
In publications with facing pages, the outside margin of each page should be double the inside margin.
For best appearance, margins should be sized progressively from smallest to largest: inside, top, outside, bottom.
These proportions can produce many different looks. In this second illustration, the page size and the proportions of the margins remain the same as in the first but the margins are wider overall, leaving less area for text and graphics.
Although you should never let strict formulas keep you from finding the right balance of margin to printing area, they can provide a convenient starting point. In the two spread examples, the margins follow these proportions:
Inside to Outside 1:2
The inside margin is 1/2 of the outside margin.
Top to Bottom 1:2
The top margin is 1/2 of the bottom margin.
Inside to Bottom 1:3
The inside margin is 1/3 of the bottom margin.
Outside to Bottom 2:3
The outside margin is 2/3 of the bottom margin.
In addition to finding the perfect fonts and moving graphics around on the page, give careful consideration to the margins of your next project. Try decreasing and expanding the margins to achieve different looks. It may be empty space but it can throw a design completely out of balance or bring it into focus.