There are a lots of ways to get the word out about your new book without bombarding friends and fans with "buy my book" posts. Here's my list of some underutilized resources.
Alumni Newsletters - Most alumni groups have a section for graduate news. Make sure to submit your acceptances and awards. Many clubs, sororities, and fraternal organizations groups also have space for this in their newsletters. Make sure that you word your announcement as news and not a sales plug.
Professional and Service Organizations - When my professional organizations or my company's annual giving campaign have service projects as fundraisers, I donate a themed basket with my books and swag.
Volunteer - Our writers' group gets calls from local libraries and book groups for speakers. They want authors for workshops and special events. These usually come with opportunities to sign books. Plus it's a great way to build relationships and meet readers.
Join Forces - Partner with other writers to share book and content information. I've also seen similar writers host contests and online events. Your reach grows exponentially when there is a bunch of you.
Expand Your Platform - Use social media to expand your reach. Build Pinterest boards for your books. Add your book events and speaking engagements to your LinkedIn profile. Post photos of events and your book signings on Instagram.
Writers' Groups - Join a professional writing group for your genre. They have lots of resources for promoting your work. Mine has a tweet network for retweeting and sharing author information.
Take Pictures - Take photos of things you do, at writing events, at others' events, and at your book signings. People like to see themselves, and pictures generate discussion and shares on social media.