Unshleved has this pdf booklet for BEA about what librarians and booksellers want publishers to know. It's great! I agree with everything. I especially want to "amen" the stickers one and the one about a synopsis. I suspect the one about the dust jacket also relates to having a synopsis. Books without a synopsis will not check out, no matter how great the cover is (case in point: Madapple). I'd like to add these:
1. Put the volume number high on the spine so it won't be covered up by spine labels or other stickers we use. This is especially important for manga.
2. Make the spine appealing too. Like this.
3. If a book is in a series, make it clear what number that particular book is. Preferably on the cover but on the inside on a title or separate series page will also work. A list of all the books of the series in order would be appreciated.