I believe you're talking about the number of people following you back after you've followed them.
To increase the follow back ratio, you will need to work on the type of people you're following. This also depends on what kind of account you've got, how active it is, how interesting the content is and is it worthy enough to be followed?
Now, coming to the second part of the problem, you need to make sure you're following the right people. You can't expect to follow a married guy from a matrimonial website's account and expect him to be follow back. He obviously wouldn't. Hence, make sure you follow people from your niche. You can get their details by having a look at your competitor's account, their following and followers should help.