The first thing you should do when you get into Google+ is to invite people to add you to their circles. After all, if no one knows you have an account, then no one can add you either. Inviting your contacts is pretty easy.
After adding people you do know, seek out people you don't. What and who are you interested in? If you don't know where to start, you can check out my lists of photographers, authors, celebrities, Google community managers and Google insiders to follow. You'd be crazy to add everyone on these lists, so be judicious. Add people you are genuinely interested in—people you'll actually want to interact with.
Once you've added them, you should talk to them. +1 the posts you like, comment on their posts if you have an opinion, and share great posts to your own circles. This way the people you follow know you are interested in them, and they'll be more likely to follow you back.
Let everyone know what you're about, and make it easy for people to find you via the Google Profile search. Turn off the privacy settings for the parts you want to be public and upload a nice picture of yourself. Also, write a mini-bio. Think of your ideal audience and describe yourself to them—who you are, what you do, and what you're interested in.
Add yourself to the many sites that are indexing and tracking Google+ users for more visibility. Social Statistics is the most well-known of them, and you can track how many people have added you over time and where you rank compared to the most popular Google+ users. Other sites include FindPeopleOnPlus, and RecommendedUsers.
This advice goes for just about every website out there on which you want to establish a presence. If you don't write engaging material on a regular basis, people are not going to come back. Be thoughtful and have a point of view. You don't have to discuss controversial topics to generate conversation, but you should definitely ask questions and encourage commenters to not only discuss the topics with you, but also with each other.
As you read your stream, you're going to inevitably come across other people's posts who might be talking about similar things as you, only in a more eloquent manner. You might think, "Darn! I wish I'd posted that!" You can just share the post, and a new thread will be created in your Google+ for your own followers to debate and discuss.
If you want maximum exposure for your posts, share it with the public, so that anyone on the web can see your posts. You can also choose to share your posts with Extended Circles. This means that your posts will be shared with not just your circles, but also everyone in their circles. They'll be able to see the posts in their Incoming streams.
- Don't post GIFs all the time (unless you are +Tom Anderson). Do you have a point other than being funny? Most likely, people in your circles have seen your GIF already and have moved on.
- Don't feel the need to keep up with the tech circles. If you're truly interested in tech, that's fine, but if your primary interests are elsewhere, it's better to talk about what you really do love. Tell people about the book you're writing, the pictures you took, your thoughts on politics, etc.
- Don't talk about Google+ all the time. If you've got complaints, use the Send Feedback button. Your followers want to know more about you, and they probably already know all about the Google+ issues.
- Take advantage of the other features of Google+. Host a hangout and tell your followers about it. Get creative with hangout ideas.
- Use the Sparks feature to find interesting articles to share. It works like a Google News Alert. Just "pin" the topics you're interested in, and click on those topics when you feel like looking for something to share.
- Respond to comments. People love attention, and when you pay attention to them, they'll respond in kind.
- Be polite, and establish your own rules of conduct. It's your space and you can take advantage of the handy "Block user" feature.
- Mention people in your posts by using the +name function, so they'll get notified when you've been inspired by them or want them to respond to your post.