This is another subject that is covered daily here. You might want to read a few pages of posts, or do a search.
But in short:
#1 Wait for readers to actually write one. Note: Reviews from family and friends will most be removed, as it's against the rules.
#2 Send the book to review blogs. This is getting harder and harder to get results from, as they are overwhelmed with requests.
You can offer the book on free promo, but that tends to bring low-star reviews, if any, and with only one book, downloads and subsequent sales are likely to be low. You also have to do some sort of marketing or promotion, or it's not very productive.
When you make a book free all the people download it, some will review it but not many, some may even read it. And you always have the, well--- let's just say the few that want's to be smart asses and don't care what they write rather they read it or not. So if your book is not what a real reviewer wants to read, then you most likely will not get a review. I'm happy with a 3 or 4 starr if they say something about the book. However some 1 starr reviews are from someone who just wants to belittle you or downgrade your work because you have wrote a book in the same genre as theirs.
I have just waited until someone want's to review one of mine and been thankful for the review. They are slow coming but I have a few. Now watch I'll get some real dilly's, for what I've said, but I don't give a da--, or care. I like a plain spoken person, and don't like a bunch of frosting.
People are more likely to read outside their genre--and then not like something because hey, they don't like that genre anyway. I saw a review like that once on some Harlequin romance that ended with the reviewer saying "But I don't like romance novels in the first place."