Authors should always refer first to guidelines provided by their editors for preparing manuscripts. Some publishers also post general guidelines on their websites.
Digital Art Submission Guidelines
While your editor may provide more detailed instructions specific to the publisher or your project, these guidelines for preparing and submitting digital images were developed by a committee of nine university press production managers to outline standards appropriate for graphics to be included in print books. The AAUP Digital Art Guidelines are the basis of many publishers' own guidelines.
Download the Digital Art Submission Guidelines