Last month, I made GIFTED, A DONOVAN CIRCUS NOVEL, free for 3 days to celebrate my new release WITCH HEARTS. I spent weeks beforehand preparing a strategy, figuring out how to promote it, and goals that would hopefully be achieved during it. The hard work paid off, because I had over 20,000 downloads, stayed at #5 in the Top 100, and even got new reviews out of it.
So I signed up for the KDP program and scheduled out my 3 free days for GIFTED. Many people differ on when to host your days, but from my research, you get better sales days (actual purchases) on the weekend, so perhaps in the middle of the week would work better. Because WITCH HEARTS released on a Tuesday, my free days for GIFTED ran on Tuesday, Wednesday, and Thursday. Tuesday was my biggest download day as that's when my scheduled promos through various sites posted them. I still had plenty of downloads Wednesday and Thursday, but there was a distinct plunge of downloads by the last half of Day 2.
Anywho, the email that went out about GIFTED on the first free day compared the story to The Hunger Games trilogy, a comparison that both tickled and terrified me. Regardless, I will absolutely use BookBub's resources for all future advertising, especially on free KDP days. It's worth the price, assuming you've got a decent marketing budget.
The Author Marketing Club has a page here for authors looking to submit their free KDP days for promotion. If you scroll down and click on the list of logos, it brings up a window where you can enter your information – just make sure to do it ahead of time, say at least a week, so you're guaranteed to have it listed (plus, it's just polite AND keeps you from going crazy at the last minute).
I also used a bit of marketing help from thedesertgirl on Fiverr. For $25, she promoted my days to several sites I wouldn't have known about otherwise. I was happy to pay the small fee for her to handle it, since the day my sales started all I had to go was log in to see she'd tagged and promoted me with several book listing sites. I will definitely use her again for future free book days.
I took out a Facebook ad too, promoting a post about the free download days. I think I put in maybe $25 – I got a ton of new fans for my author page and feel confident it converted into at least a couple handfuls of the 20K+ downloads.
I would absolutely recommend checking out these links for other advice too. They not only list great links for where to submit your listing, but also offer tips on when to choose your days, how to promote through social media, and more.
Before your days, make sure to submit your listings to all of the sites you can find like these (Pixel of Ink, Free Booksy, etc.). I also have amazing friends (authors and readers alike) who shared out my posts on Facebook and Twitter, hosted me on their blog for the day, and/or promoted it however they could. Next time, I hope to better implement a hashtag on Twitter (#WitchHearts/#Gifted) that will catch on with any of my communities.
On the day of, make sure you're posting on all your networks! Use your Facebook fan page to your advantage and talk it up. Same goes for Twitter, Google+, LinkedIn, etc. Write up a blog post announcing it and make it live that morning so it reaches your fans and followers early. Ask your fellow writing groups and author contacts to share it out (and make sure to offer to repay the favor for them). And for all that is holy, thank every. single. person. who shares, RTs, and helps to promote YOUR product. We wouldn't get far without them.