Such a great question, and one that I spent a lot of time trying to figure out with the last four books that I published. There are several ways that marketing a book can be done, but only a few ways that make the process fairly simple and give you the results you want.
Wattpad is a great way to test out your chapters and build a following online. When you create an account and profile with them you have the opportunity to publish your book one chapter at a time, two chapters at a time, or the whole book at a time.
What you'll find as you build a following is people are anxiously waiting for you to publish new material, and you can easily direct them to any published works on Amazon and other platforms such as Kobo or B&N,
You will still face the same challenges on Wattpad that you do on any other platform when it comes to building an audience, and growth can be slow, which is why I always recommend that you build a loyal list of subscribers so you have a built-in audience to promote to.
I've sampled plenty of authors' newsletters, and many of them will offer sneak peeks and first chapters to their fans who are eagerly waiting for the author's next release.
Not only does this engage their audience by asking them for feedback once they have read the sample chapters, but it builds buzz for the release of the book, and if your subscribers go so far as to share the chapters with others so much the better.
Pre-testing chapters can also be done with a launch team or street team. This is a group of people who have signed up to review your ARC (Advance Reader Copies) and give you feedback on your latest works. They also help get the word out about your book through their social media accounts and through the reviews they leave for your books on Amazon, Goodreads, etc.
My launch team does a stellar job of reading my books and having reviews ready to post on release day. This is how I am able to get up to sixty reviews within a week of a book's release. I also have a large mailing list of eager fans who want that next book. So my marketing always includes that built-in audience
So yes! Pre-testing chapters on platforms that allow for this can get you some great exposure, but using this strategy with an actual list of loyal subscribers is a far better way to tackle that particular marketing strategy.
Yes, you should absolutely pre-test your chapters, and it can be a great way to market your book.
I'm not personally familiar with Wattpad, and it looks like activity is sparse for my genre. I instead tested my book directly to my audience, and it helped a lot with marketing.
Here's exactly how to test your content and market your book in the way that I did in order to write "The Heart to Start:"
1. Publicly announce a writing challenge for yourself. I set up a landing page with my outline, and promised a chapter a day for 30 days to anyone who signed up to my email list. ConvertKit is a good email marketing platform for authors, but I use ActiveCampaign, despite it being much more complicated. I have some content online about why, if you run a search.
2. Do the writing challenge, emailing chapters or sections to your readers on the planned schedule. Ask for feedback at the end of each email. It's okay if you write ahead of schedule to take some of the pressure off. I personally scheduled the following week's emails at the end of each week.
3. When your first draft is finished, put it on a Google Doc. Allow comments from anyone on the doc (but not editing). Send it to your email list and tell them you'd love their comments and edits. (You can do an edit before this, as well). Tell them you'll put them in your acknowledgements if you use one of their edits. If you're lucky like me, there will be discussion amongst readers on your book, and you'll get a good free editing job.
4. When you launch your book, you now have a bunch of people who have already read it. I personally offered my book for free for the first several days. At the very least, put it on Amazon for free just long enough for those early readers to snag a copy. You'll see why in a second.
5. Ask your early readers for reviews. They've already read your book, and if they picked it up for free on Amazon, they're now in the system as "Verified Purchases." When they review, it will say so next to their names, which makes their reviews more effective.
There you have it. Yes, those first readers got your book for free, but you got feedback, editing, and Amazon reviews out of it. That's more than a fair trade!
And that's a good best practice for marketing your book. The rest depends upon your genre. As a non-fiction author, I try to get on podcasts and write blog posts as well.
I hope that helps. Feel free to book a call if you have questions about details.