1. Use hotkeys to get around Google+ faster. In your Stream, press "j" or "k" to move through posts, and press Enter to start a comment. (Pressing Tab and then Enter will cause your comment to be submitted; hitting Tab twice and then Enter will cause it to be cancelled.) You can also press "q" to jump to the Google+ chat box.
2. Hotkeys work in the notification drop-down, too: Press "j" or "k" to move up or down in the list, and then press Enter to open any individual notification. When viewing a notification, "j" or "k" will let you progress forward or backward to other items. Pressing "Esc" will close the notification window altogether.
3. Want more hotkeys? Check out the G+ Extended extension for the Chrome Web browser. It adds a series of additional options, including hotkeys for +1'ing posts, sharing posts, and expanding comments.
4. If comments are getting out of control in your Stream, try the +Comment Chrome extension. It collapses all comment threads so you see them only when you click to expand. Another good option is the G+me Google+ extension; it leaves comments expanded by default but gives you a one-click option to collapse any thread or post on demand. It also provides badge-style comment counters to help you keep tabs on new activity for items you've collapsed.
5. You can take a specific item entirely out of your Stream by clicking the small drop-down arrow next to it, then selecting "Mute this post." That'll also keep you from receiving any future notifications about the item.
6. On your own posts, that same drop-down arrow holds options to shut down comments and prevent people from resharing. The commands affect only the specific item you're viewing.
7. Sometimes leaving a comment on an active post can turn into a bouncing-screen challenge, thanks to the top-of-page activity always pressing your Stream downward. To solve this, click the drop-down arrow next to the post you're viewing and select "Link to this post." That'll open the post in a new tab; type your comment there, then close the tab when you're finished.