Once your book is out, you need to spread the word as far and high as you can. You can reach your network, but unless the book goes viral through word of mouth, that network will run dry after a few hundred (or thousand, if you're really popular) mentions. And of those mentions, only a very few people will buy the book at first. It takes time, patience and perserverence to see the book to even moderate success.
One way to boost sales, and to at least remind people that your book exists, is to get reviews. Space them out. This way, when you get a new review, you can post it for your network to read, and they won't be spammed with 30 reviews in a day, then hear nothing about it again. You'll effectively remind your friends without bothering them. Amazon and Goodreads reviews can make or break a new author, so make sure to keep checking for them.
Search out review blogs. When someone who doesn't know you reviews the book, they open you up to their network, adding it to your own. This is so important.
There is a certain protocol when asking another person to take time out of their life to read your book and write about it. Remember, they're doing you a favor, whether they like the book or not.
HERE'S HOW TO DO IT: