One of the distinctive features of Google+ is that it lets you disable comments and lock down posts from sharing, but so far, you were only able to do it after you share a post.
Now, you can do it before you share, which makes much more sense; after all, if you don’t want anyone to comment on or share your post, you probably want it that way from the start.
http://mashable.com/2011/10/05/google-plus-lock-down-posts/