As you continue to use Google+, your circles will begin to fill up. There is currently a limit of 5000 people allowed in your circles, read on as I've discovered two useful ways of clearing out your circles when needed.
Using Two Great Chrome Extensions
I've chosen these two extensions because I have used them in the past and they have been very effective. Back when Google+ launched I was quick to find out that I had a lot of inactive users in my circles, so I regularly made use out of the extensions. Hopefully you'll find them useful too!
Introducing - Circlescope Free (Inactives+)
Once Circlescope Free (Inactives+) is installed, it will search through your circles and find people in them who haven't posted for a certain amount of time (you can decide on this amount of time and various other options within the extension). Once selected, you can then remove these and add some more active users on +Google+!
Using the Extension
To get started with the Circlescope Free, just click its icon located in the top right of the toolbar in +Google Chrome. A drop-down will appear with your display name on Google+ which you will need to click on.
Click this button, located in the top-right of the page:
The tour will then guide you through the extension, and you should soon be able to uncircle any inactive members in your circles. Circlescope Free allows you to set the amount of time to check the people in your circles posts for - the more recent the time the more people it will consider inactive. I recommend setting the time to about 6 months back.
You can also choose which circles the extension will check, so make sure to remove any important circles such as 'family' to avoid removing anyone important! You will be able to review everyone who is going to be removed beforehand and un-check people you wish to keep in your circles, so make sure to scan the list for anyone you would like to keep.
If you think you're ready to go then hit the download button below (Google Chrome only).
Introducing Circlescope Free (Uncirclers+)
This extension was also developed by +Ehsan Ahmadi Gharacheh, and will allow you to remove people in your circles who haven't circled you back. Remember that most pages and celebrities won't follow you back, so make sure not to uncircle them if you are still interested in what they're posting.
Using the Extension
The extension is very similar to Circlescope Free (Inactives+) and can be installed using the button below. To start, click on its icon and then click on your name.
You will then be presented with a similar page, again you just need to click the 'Take the tour' button located in the top right of the screen.
I'll say it again, this extension will allow you to choose which circles to check and provide you with a list of all the people you are planning to remove so please make sure to uncheck anyone important. Personally I think this extension is less useful as a large amount of people who haven't circled me back I still want to follow - so bare this in mind when using it.
Using these extensions, you should be able to remove a significant number of people from your circles if you need to clear out some space.