Write a query letter. The letter will be what you use to get an editor, publisher or agent interested in your book idea. The query letter should be crafted in a specific format to give it credibility. It also ensures that the letter has all of the elements that the reader will need in order to make a decision about the book idea.
Create a query letter that captures interest right away. The editor who reads it should come away form it believing that it is a unique idea that has the potential to interest a wide audience. The query letter should start with a sentence that is carefully crafted to bring the book's most exciting concept to the editor's attention.
Put together a book proposal for publishers that require them as part of the process. A book proposal includes a few sample chapters, a chapter-by-chapter synopsis of the entire book and information about the target audience and the current competition. Demonstrate that the audience is wide enough that the book can be a commercial success and that there is not too much competition for that audience.
Follow all directions given by the publication. Sometimes this means that no email submissions are accepted or the submission must be on disc. Sometimes an agent is required to submit the book idea before an editor or publisher will look at it. If the directions are not followed and the requirements are not met, the book idea will have little to no chance of ever being accepted.