A drop-down menu lets you choose which circles you want to share your post with.
When you're ready to share something, click the large "Share what's new" box at the top of your Google+ stream. You can then type in any text, paste in any link, or attach any photo or video using the on-screen commands. When you're done, click inside the large white "To" box -- where it says "Add names, circles, or email addresses" -- to determine who will be able to see your post.
You can select one or more of your circles or add in the individual names or email addresses of anyone you know (if the person doesn't already have a Google+ account, he'll just receive an email with the content you shared). You can also opt to share to "Your circles," which will make your post visible to everyone you've added on Google+, and to "Extended circles" to share it with friends of your G+ friends as well.
(If you're already viewing content from a specific circle within Google+, the system will automatically set your post to be shared to that circle; you can always change it, however, and add additional circles or individuals to be included.)
If you want a post to be publicly accessible, select "Public." That'll make it so anyone can see your post; it'll show up with your name in searches within Google+ as well as in regular Internet searches through any Web search engine.
Note that if you opt to share a post with only a limited group of people instead of sharing it publicly, Google+ won't let anyone else reshare your post to Public -- you'll have to share it with one or more of your circles from that point forward.
Want to mention another Google+ user within a post? Simply type + and then start typing her name; the system will give you a list of matching options and fill in the rest for you. This will cause the person to be notified that you mentioned her and also allow other users to hover over her name and learn more about her.
When something happens on Google+ that's directly relevant to you -- like someone mentioning you in a post or commenting on one of your posts -- the system will give you a notification to make sure you're aware.
Notifications are accessible by clicking on a bell at the top right of the screen.
Notifications are accessible by clicking on a bell at the top right corner of the screen. When you have new notifications, a small red box appears alongside the bell with a number to show you how many are pending. Click on the bell to view them and see what's going on.
You can also opt to receive certain types of notifications via email or text message, if you'd like. To do so, you'll need to go into your Google+ settings. You can get there by clicking your name or image at the top-right of any Google service and selecting "Account," then "Google+."
You'll find a host of settings there, including options to limit who can cause notifications to be sent to you and a list of specific notifications you can set to be delivered as emails or texts.