6. Promote Your Google+ Page
To build a follower base, it's important to promote your page in a variety of ways. Mention your Google+ page in email broadcasts, add the +1 button to product pages, include a link on product receipts and email signatures, and reference it in offline promotions such as direct mail.
7. Interact with Pages and People
The best way to get your followers to engage with you is to engage with them. When someone comments on your post, be sure to respond in a timely manner. It's also helpful to follow those who follow you.
In addition, a Google+ page can add other pages to circles (see #7). A good practice is to follow other relevant, non-competitive businesses, as well as businesses with customers similar to yours. The more you engage with these pages, re-sharing and commenting on posts, the more visibility you will get in their followers' streams.
8. Segment Your Audience Into Circles
Circles is a core component in the Google+ platform that enables you to segment followers by geography, gender, age, or whatever criteria are important to your business.
When posting content, choose circles that would have the most interest and be more likely to respond. Note that people must first add your business to their circles before you can add them to your own.
9. Launch a Google+ Community
Google+ recently launched a new component called Communities, which resemble Facebook and LinkedIn Groups. Communities tend to be topically focused, so content shared within them should not be overtly promotional. Still, such communities can help grow awareness of your business, which can lead to more followers.
My article "How to Create a Google Community" outlines the steps for how to set up a community.
10. Track Page Activity Using Analytics
Google offers two ways to track activity that takes place on your Google+ page to help you understand the effect interaction has on website traffic and sales conversions.
Google+ Ripples is a data visualization tool that shows you who shares and then re-shares your posts most often.
Ripples makes it easy to identify and follow key influencers, and learn what content is most compelling to their audiences. Use it to spot trends and track the spread of posts over time, or see how a post was shared.
Google Analytics offers a feature called social reports that shows how Google+ influences your conversion funnel, the impact of personalized recommendations on your site, and what visitors from social networks are coming to your site to see. You can also login to AdWords and see AdWords Annotation Reports, which show how ads with Google+ annotations compare to standard ads.
Social reports help you measure the impact social media has on your business goals and conversions.
Due to its growing popularity, the positive effect it can have on search returns, and its ability to directly connect businesses with customers and prospects, Google+ is a social network merchants should consider adding to their social media outreach activities.