Talk to your followers
The 'social' part of social media is often overlooked - meaning it's easy to let your Twitter feed stagnate into a stream of 'look at me' ego-massaging that's as boring as it is repetitive. So make sure you keep your followers engaged - retweet their stuff, offer up 'Follow Friday' suggestions (hashtagged as #ff), strike up conversations and reply to direct messages; it makes your followers all the less likely to unfollow you, and they may even recommend you to their followers.