FOR #FILIPINOAUTHORS - THE POWER OF FREE

I've been asked several times about why I have so many FREE books (of course, I've also been asked why I don't have ENOUGH books that are free, but that's another story :D).
Anyway, what I'm about to share is nothing new at all. You can check out other veteran indie authors' blog posts and they'll tell you the same thing (and probably even more). I've also discussed this a few times in the past, I think, but in any case, I just thought I should write my own in-depth post about the power of free to show how free books as a marketing tool can also work for Filipino authors like you and me. 
Please note: 
All screenshots below were taken around around 3 to 4AM EST, May 7.
All screenshots are based on Kindle (Amazon) sales. If I can find some free time again, I'll try to share graphs based on B&N and iBooks sales.

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So, anyway, a few days earlier I set the prequel to my recently completed serial The Greek Billionaire and His Secretary (prequel’s title is same as the serial’s). 
Below is the graph of how the prequel performed in the >2 months it's been out.

Now here’s the same graph with free units included. It went free May 4. I did a bit of advertising on FB on May 5.

Now, here's what happened to Book 1 Dear Greek Billionaire when the prequel went free. You'll notice that sales started climbing up May 5. 

And then Book 2 Love, Your Greek Billionaire...

Now, Book 3 Forever & Ever, My Greek Billionaire also went out May 6. We can say, for the sake of argument, it may be the fact that the series is complete that drove sales to Books 1 and 2. 
But that's not the case at all. When I look at my graphs, I saw that my first-day-sales for Books 1 to 3 are virtually the same. If Book 3 is the reason that I have new readers snapping up Books 1 and 2, there should also be a significant increase in the sales of Book 3 (I should also note that, because of the length of my books, a reader can finish all three (or four, including the prequel) in one day).
If I have enough time, I'll try to post another set of screenshots to show the effect of free books on sales past May 6. But for now, I hope we can at least agree that free books CAN drive sales.  

Advertising free books

Doing paid marketing for free books is optional. When my book went free on May 4, there were already people who downloaded the prequel without me doing any marketing, enough to get the book to Top 500 overall for free books on Amazon. But I still like paying for advertising because - at this point - I feel my time is better spent writing than doing marketing. But I have done my own marketing in the beginning, with good results, so it can be done. 
Now, because I did pay for advertising, some of you may question whether I was able to recoup the money I spent on advertising. (PREPARE YOURSELF. CALCULATIONS ARE COMING)

Step 1: I calculated the average number of copies sold per day between April 27 to May 3 (last 7 days of sales before the prequel went free on May 4) for DEAR GREEK BILLIONAIRE and got THIS NUMBER.

Step 2: I then calculated returns that can be attributed to the prequel going free.
May 6 Royalties - (THIS NUMBER x Royalty Per Book) = Profit #1.

Step 3: Repeat steps 1 and 2 for LOVE, YOUR GREEK BILLIONAIRE.
May 6 Royalties - (THIS NUMBER x Royalty Per Book) = Profit #2.

Step 4: Calculate how much I still need to earn to recoup my advertising expenses.
Advertising Expenses - (Profit #1 + Profit #2) = Balance

Based on my calculations, I already earned back 57.90% of what I spent on advertising on May 6. 
Based on past experience, I think I need about 2 to 4 days more to earn the back the rest. 
Everything is pure profit after that. :D

WHICH BOOK TO SET FREE AND ALSO YMMV

One thing I should spell out is that, obviously, all these books are under ROMANCE. Not sure how the numbers would differ for other genres but if you check out Russell Blake and J.A. Konrath's blogs, I think it's safe to say that free books helped them a lot, too. 
Also, it definitely took longer for me to recoup paid advertising expenses in the past. I was a newer author, I had fewer books, and I made a couple of rookie mistakes. So...bottom line, YMMV. 
However, I believe you can improve results on setting your book free with the following:

• If you have a series / serial, set Book 1 or the prequel free.
• Cliffhangers can get you lots of love and hate. I personally love writing them, and though you could get a lot of flak of it, there's also nothing like a cliffhanger that gets readers to one-click faster). In my part, I try to give readers a heads up in advance about it. For The Greek Billionaire and His Secretary, I warned readers that there's heartbreak ahead (they rightfully equated this to cliffhangers) and it will be so until the last book.
• Set the book free once you've completed the entire trilogy (especially if all the books revolve around one couple) or you've written at least 80% of your series (say, Part 4 in a 5-part serial). I learned this from Liliana Rhodes, by the way.
• Make sure you have all the links available in your front and back matter before setting the book free.
• Experiment with covers and blurbs for Book 1. 
• Do marketing (paid or free). There are all sorts of things you can do, and you may have to experiment with each (a.k.a. trial by error) until you find out what works for you.
• If you're writing a series of standalones, you can switch it up. Let's say Book 1's free for a year. You can get it back to paid then make Book 2 free. I learned this from Cora Seton, although I forgot if it was from an article or podcast.
• Some authors give readers an added incentive for clicking the sequel by pricing Book 2 at $.99 then the rest at $2.99 or whatever their regular price is. I haven't done this yet, but I heard from other authors that it worked for them so I thought I should share this tip as well.
• Have it available on as many retailers and websites as possible.

And that's it. I hope this helped! :)

NOTE: EVERYTHING YOU'VE READ IS MY OPINION ONLY. You are not obliged to think I'm right. 
I am 100% aware that these graphs don't take into account all factors affecting book sales, etc.