BookBub's "Ask an editor" installment answers granular Featured Deal questions - category fit, price windows, cover specs, timing - pulled from real submissions that get rejected for fixable reasons.
If you've ever stared at the form wondering why similar books get picked, this is the closest thing to a checklist from inside the house. It won't guarantee a yes, but it cuts down self-inflicted nos.
(Shortened and summarised to avoid devaluing the source)