There are five basic ways to be active on Google+. These are demonstrated below.+1 a post, a comment or a reply. A +1 on a post will display your profile pic as having voted for it. A +1 on a comment or reply will show as having been voted up (see red counter).
Comment on a post. A comment to a post displays below the original post.
Reply to another member’s comment. This inserts the name of the person to which you are replying at the beginning of a response.
Share a Post. It is easy to share posts from your stream with your Circles or in Communities using the Share button.
Compose a Post. You can see a slight difference in the post box when you are posting to Public or your Circles versus to a Community. In a Community you don’t have to direct the post to someone, rather you post it to a category. Both posts offer the same embed options (you can only embed one link although you can include multiple links in the body of the post).
For more on Getting Started and Engaging in Communities, visit this Google Doc.