So you've got your Google+ Page and Profile set up and "optimized". Now you need to post something. It can be tough at the start (and even later on), so here's some ideas for you.
Google+ is made for images. Whether that's Photos, Cartoons, or even animated Gifs, Google+ provides a great platform to showcase images. You can upload a single image, create a gallery and even have some fun with Google's built in Creative kit and Meme Generator, but don't forget to give credit!
bonus: don't forget to title your images. It helps people find them.
2) Latest News
Are you a news junkie? Just read a great article on a breaking news story? Share it! Everyone loves to be up to date and a fresh news story will always be popular.
bonus: use the Google+ search feature to find the latest news.
Who says you have to do all the hard work? There's tons of great posts out there waiting to be reshared. While you're waiting for your inspiration to hit, go and help someone else out by resharing their post.
bonus: leave a +1 to say thanks!
We live in a "multi-media" age right? Why restrict yourself to pictures and text? Record a video and share it, or share a great video that you've found.
bonus: uploading your own video fills up that Video tab on your profile that you never use.
5) Go Niche
Can't find enough interesting posts on that thing you love? Sounds like an opportunity! There's probably loads of people looking for that thing as well, so post something on it.
bonus: don't forget to #hashtag your posts for easier discovery.
6) Be Trendy
If a topic is popular, then get involved! Get your opinion out there. (Google+ gives you plenty of room, no 140 nonsense) There's a list of trending topics on the right-hand side of the search page.
bonus: doing a search for something brings up a Post box with "join the discussion about...." Post using that box and you'll be placed right into the search stream for that topic. Great way for people to discover you.
Good luck and remember to have fun.