What You Are Selling is Never as Important as THE REASON SOMEONE IS BUYING IT.
Let's look at how people choose a book?
e) Sympathy & friendship
Is your cover enticing?
Does it whisper at what's inside?
Does it create a feeling for the prospective reader?
Is your title easy to read?
Unless you're a graphic designer, book designer, I would suggest that you don't spend your time doing what will take time away from editing your book. Let an expert do what they do best. Give them a brief of what you like in covers which will cut down their time and cost you less.
Cover these points and you have passed the first hurdle.
Have your told your story in a nutshell without giving away the ending?
Have you made it sound thrilling?
Its a good idea to ask your writing friends to read your blurb and suggest any changes to make it better.
Also, look at key words in your blurb. This helps when readers are searching certain key words such as #thriller, #crime, #fantasy, #romance #ScienceFiction.
Gaining reviews is the bane of every author.
Gift your book to people and ask for an honest review (and I mean honest).
If you get an honest review from someone you gifted your book to. Take note and make any changes to make your book better.
There is no limit to the number of times you can tweek your book on Amazon.
If it's a substantial edit, then you can notify Amazon and they'll notify all customers who have previously purchased your book about an update.
If you have no reviews, then buyers are hesitant to take a risk on your book unless it's on sale. Therefore, do not price it too high. Usually, $2.99 is a good price point.
I took out the Table of Contents in my book because it meant that in my book preview on Amazon I got a couple of extra pages when a reader clicked on the preview of my book. However, for non-fiction you will need that TOC so this won't work for you.
Post a longer preview on your blog or web site. Tweet that they can find the longer preview there.
e) Sympathy & friendship.
Now some people may wonder about this point.
Put simply, it means that someone you know will buy your book because they don't like to offend you or feel sorry for you.
But a sale is a sale and helps lift your rating on Amazon.
Those of you who constantly post buy my book in the writers Facebook groups? Does it really work? For the most part, this only gets annoying and turns people away. So initially these authors gain sales, then people turn off every time they see the post or start deleting it.
Your book is on sale or free your rating goes up.
Some readers buy a cheap book because it's on sale but they don't read it and don't leave a review. Amazon knows if said book has been read and what percentage it's read with is reflected in its rating.
This works for the short term but long term you want reviews and word of mouth recommendations.
How do you get these?
Writing the best book you can.
Having said book edited and getting a great cover made. If you're unsure about your blurb, ask your writing friends to look it over and suggest what you can do to make it better.
Some authors will say that cheap/free works or free for them. However, you can't put money in the bank with free.
Once you have a small amount of reviews (say 10), you can experiment with pricing and put you book at a higher price and see if your sales fall. If they do, you can lower the price. Or you can lower your price on certain days and see what happens. Make it fun and make it work for you.
Promote your book on as many sites you can. No one knows of your book and your book is but a drop in the ocean of books.
Use social media to do this.
If you don't know how to do this. Just start with twitter and start following people.
Remember, your twitter profile is your public face. Likewise your web page, blog, etc.
Have pictures of your book there. Include links to your book on twitter, your website and anywhere else readers can buy your book.
P.S. Don't forget to tweet regularly. Also, follow those that follow you. You ignore followers at your peril.