A few tips below will help sharing on Google+ contribute more actively to your SEO plan:
Sharing by only paste the link into the post is inefficient. Sharing links with headlines would gain more attention of others, increase the chance people actually read what you share. You can check out Google+ format cheat sheet to help your posts look more intuitive to users and more attractive to search engines results.
Instead of just sharing the link on Google+, you should write a short description for your article to help others catch the main ideas. A focused description would make your articles look more legit and resourceful. Also, you should upload your own photo instead of using thumbnail from shared links.
Unlike Twitter and Facebook, Google+ use #hashtag to organize and allocate relevant contents, so choose the right Hashtag content and don’t spam too much.
Placing Google Comments on articles to be good for optimizing SEO and Google+ SEO of those articles. Better results would be achieved when you should post your own articles embedded with Google comment.
Source: Consolidate from many SEO resources.