Favorite Black Friday Marketing Techniques

For most years, I’ve run very basic deals on Black Friday: 20-25% off physical books and price drops on ebooks. It goes…okayish. But I suspect there are more tactical ways to go about deals. Like adding in free shipping (because no one likes extra fees) or bundle deals. Do you have any favorite marketing techniques and/or dates (sending marketing emails on BF vs a week or two before)?