Ensure the manuscript (including any appendices, bibliographies, acknowledgements, etc.) is a single Word document (.doc or .docx).
If you have imagery or illustrations please make it obvious in the manuscript where these should be placed together with a name for the image which matches that image’s file name (a thumbnail or low-resolution version can make this particularly clear).
Name the file clearly so it is obvious who the author is and what the book project’s title is.