It's a fact that every author has to accept and deal with: more reviews equal more book sales. Most experts estimate that the average book will get one review for every hundred books sold, but this will vary greatly, depending on your genre. Some fans simply leave reviews more often than others. Regardless of the niche you're writing in, getting more reviews will be a constant battle and an important focus in your marketing plan. Obviously, worldwide bestselling authors will find the process much easier than those with only one or two books published, but you should start seeking reviews from your readers before you even publish your first book.
Your Insider Team
Before you publish your first book, you should begin to gather fans of your genre, priming them to eagerly read and review your book. Look in genre-specific Facebook groups to find people who love books like yours, and ask if they'd like free copies of your book in exchange for an honest review. These free books, called ARCs (Advanced Reader Copies) are meant only to be given out before your publishing date. Once you have your ARC team established, send out a copy of your book about two weeks before the publication date. That will give them plenty of time to read the book before dropping a review on or shortly after your launch date.
Your Book's Back Matter
It's surprising how many readers never even think about writing a review, even if they've loved the book. The simple act of asking for a review can stimulate some fans to click right over and post some great opinions. Your book's back matter is the ideal place to put this request. The first thing your reader should see after the phrase "The End" is a request for a review and a link to your review page. Ask nicely, explain how important reviews are, but make it as easy as possible for them to do it.
Your Website
Every author needs a website. It's your business card online. And every website should have multiple opportunities to click over and leave a review. If your fans are interested enough to look you up online, they're probably invested enough to spend three minutes leaving you a good review about the book they liked.
Review Lists
Amazon keeps a list (updated every two days) of the most influential reviewers on their site. You can dig through that list of 10,000 reviewers to try and find those who specialize in your book's genre, or you can pay someone to do it. Keep in mind that this is definitely not paying for a review. That's against Amazon's rules. Using a company like BookRazor is simply saving time and allowing them to do the detail work in finding already-public names and emails. Once you get a list of names, send a personalized note to each one of them describing your book, and ask if they'd like to read yours free with an eye to leaving a possible honest review. Top reviewers never pay for books because they have authors send them free all the time, but if you catch the eye of some of the review stars in your genre, you'll be on your way to big sales.
Book Bloggers
The key to getting great results with book bloggers is to build a relationship long before you ask for a review of your book. Find the most influential bloggers in your niche and start frequenting their blogs. Make intelligent comments and let the bloggers get to know you. The best bloggers have more books offered than they could ever review, but if they see a book from someone they know is a true fan, they're more likely to give it a look. Many bloggers never post reviews on Amazon, but they're so influential they'll encourage other readers to do so, many more than you could contact on you own.
Review Swaps
You're in a couple of genre Facebook groups and you all need more reviews for your books. Why not buy each others' books and leave honest, legitimate reviews for each other? If you ever come across someone suggesting this in a group, back away quickly. This is against Amazon's Terms of Service and can endanger your entire KDP account. And yes, Amazon has people who search through Facebook and other social media sites, just looking for violations like this. It's not worth the risk; don't try it.
Keep the Faith and may the Force be with You!