1. Always judge a book by its cover. You wouldn't get into a taxi with battered body work to go to a dentist with bad teeth, would you?
2. Aim for the heart, the head, and then the wallet. In that order. A weak book, badly designed won't sell at the cheapest price. But a book that promises to move and engage someone can command a good price.
3. Make sure your designs can be read quickly - you only have seconds to draw a reader in.
4. Don't try to be too "unique." If no one is doing something, a "super idea" you have had, there might be a good reason for it.
5. Say as much as you can in the fewest words. Cut out all the stuffing. Remember, give your reader the prime cuts, because you want them to come back for more. If you fill their plate with fat and gristle they will tire of chewing.