Make sure you are making worthwhile posts. Matthew Inman made a fantastic guide about what not to post: http://theoatmeal.com/comics/twitter_stop
Be active on your twitter and share the stuff which they were engaged so it help to get new active followers people you follow they follow you back once you unfollow them they will do the same this happen simultaneously or don't use any third party website to increase followers bcoz they might be fake followers
Twitter users or Tweeples used to unfollow accounts for several reasons. But most of the time, they unfollow accounts that are not relevant to their usage. Most of them find it difficult to handle if there are a lot of feeds, or sometimes no posts at all. That is why you need to continue engaging with your followers and give them what they need or some posts they can relate with.
Know what your network like and give them the same..Have an engaging conversation to build relations this syntactically makes your follower stay with you.