Find out-of-print books that you treasure. Any author of a forward should have a belief in the merits of the book. Remember that unknown or not-yet-established authors do not get the opportunity to write book forwards.
Write a query to publishers that you have a strong working relationship with. You should explain the value of a reissue of the book. In some cases, an older book might become of interest because of changing popular tastes or critical opinions.
Compose a brief summary of the novel. The summary should foreground the central conflict in the novel. For experimental works like James Joyce’s “Ulysses” or Flan O’Brien’s “The Third Policeman,” the conflict might be between less external and clear forces, which can be hard to render compelling.
Write a biographical sketch of the author. Search in the archives for older interviews, book reviews and previous biographical information. If possible, interview the author. The purpose of the biographical sketch is to highlight the author’s career as a writer and any autobiographical elements in the book.
Explain the social or literary relevance of the book. Non-fiction books often are reacting to or attempting to reach a specific audience. For example, Rachel Carson’s “Silent Spring” criticized environmental crises caused by insecticides and sparked the modern environmental movement. A work of fiction like “A Modest Proposal,” which assaulted 18th century British policies in Ireland, has a very specific literary relevance, as well.
Describe any personal connection that you might have with the book. This personal connection should convey why you value the book and why you believe the book is worth reading. In his forward to “Desperate Characters,” Franzen describes the differences between his first, second, third and fourth readings of Fox’s novel.
Organize the material clearly and concisely. Because the forward should be less than ten pages, conflating the material will require you to prune some good material and master transitions between, for instance, biography and summary.