You have thousands of people in your G+ circle and each of them have different kind of interest over different things, so they share different topics with people in their circle. This is overflowing your G+ stream and you want to see only those posts in your stream that match your interest. You don’t want to remove them from your circle but at the same time you don’t want to see what they posts. That’s where the # tag comes in to play.
You have used the Google+ search right? Now try to search using #tag in the same search box.
Enter #Google to see what people are talking about Google in Googleplus. Select what you want to search like – People and Pages, Google+ Posts, Sparks, Hangouts or everything. Filter it more by selecting where you want to search like – contents from YOU or content from your circles or from the whole world. You have the option to chose the location also for this search.
Once you have selected the right options you have the result you wanted to see. This will show only those contents that have a #Google tag attached with it.
More interestingly if you add your content with this search open, it will automatically a #Google tag to it.
Now you know the secret to get Google+ stream the way you want. Happy G+ing.