Google+ is a social media platform same as Twitter and Facebook so the same methods that you used to get your followers there will work with Google+. Here are a few methods I used with good results. 1) Add your friends. Just email them and ask them to join you. 2) Set Up a Google+ Group or Business Page (same as FB Fan Page) Post on it daily with keyword rich content. 3) Do a targeted search of users on Google + and add them to your circles. About half of them will add you back. 4) You can buy followers on Fiverr.com. This is quick but you won't have targeted followers. That should get you started anyway.
You can share your G+ page's gadget in your website/blog to let your site visitors know that your website's page is available on Google+. And there will be a chance for you got more followers for your Google plus page.
Here's an interesting article that lists a few, quick and easy to use tips and tricks for building better G+ brand pages and increase your followers.
Google+ starts with the basic circle and then you can create other circles of your choosing. Everything is based on Google profile as profile reflects the standard of business so it is quite necessary to filled out all of the necessary information.