This isn’t going to be an in-depth discussion about Google+. I’ll leave that to the experts. In fact, before my search tips, let me point you to two sources that provide updates on all that’s new on Google+.
HubSpot has published a comprehensive free e-book How to Use Google+ for Business. Just click on the title and you will be able to download the PDF from the home page.
The other is also a lengthy tutorial (slightly more technical) but well worth reading on Blind Five Year Old by AJ Kohn.