Google's Dennis Troper announced on Google+ that you can now, like other social networks, pin your favorite post to the top of your stream. So if you want people to see a specific post first, you can pin that post and even if it is weeks old, it will remain at the top of your profile.
Here is how you pin a post. You click on the arrow down on a specific post and click "Pin post":
When it is pinned, it will show a little pin icon on your pinned post:
This is also supported on the Android app, with iOS coming soon.
Forum discussion at Google+.
