ManageFlitter is my go-to service for managing who I follow on Twitter. It’s super simple to connect the service with your Twitter account, if you are logged into Twitter in a browser and then visit ManageFlitter in another tab it connects automatically.
It shows me how long accounts have been inactive, and who isn't following me back. You can see which profiles don’t have an image, and which accounts are likely spam. You can unfollow accounts that look sketchy or are too quiet for your liking right from within the service. You can give it a try for free to manage some basic things about your account, and upgrade to a Pro account for more features like account analytics and seeing who your fake followers are. You can also set up your account to automatically tweet your Google+ posts which is a cool new feature I am looking forward to taking advantage of.