If you sign up with KDP select, you'll be given 5 days where you can drop the price to free. You'll be restricted to only publish on their platform, however.

Hit up your email list, use sites like BookBub, or reddit.com/r/FreeEBooks in order to prepare for the discount launch. Start the deal on a Sunday since more people will be at home and prepared to read rather than Friday and Saturday nights when they're out.

Include, at the end of your book, a request for people to leave honest feedback. They're more apt to do it if you remind them. You can also include links to your other titles.

I've published a handful of titles under different pen names but I'm not an expert. I just figured I'd share what my research picked up.