I just noticed that right now in Google Plus, you can make a chat by default with your circle friend without need to add them manually or need an acceptance. Unlike others Instant Messaging, if you wanna make a chat with someone on Google+ for the first time, you need to add them to your friends list manually and then wait for acceptance from your friend. But that the old version. Today, the rule changed. You can make a chat as long as your friends is on your circle and yourself are in their circle too.
By default the privacy setting on Gplus chat set on circle base, but you can customize if you like to able it just for specific circle such as only on your closed friend or family or etc. To change the settings, click the down arrow on the chat then click “Privacy Setting” > Click the circle.
Choose custom then check the circle that you want to allow to chat with > Save the settings > Done. Now you can start to chat with anyone who already have you on their circle and you’ve allowed to chat with you. Remember the G+ Chat actually the same IM of Google Talk / GTalk, but it uses under Google Plus site and it’s not a group chat.