Unlike in real life (IRL) when you are being followed don’t run, follow back. If someone follows your Twitter account follow them back unless of course they are some weird porn site .
If someone unfollows you then you reciprocate by unfollowing them. If someone retweets (RT) you then you go visit their timeline and retweet one of their tweets.
Always favorite, retweet, or respond to every tweet you are mentioned in unless you are being trolled. Trolls get muted, blocked, and/or reported.
80 20 Rule
You should follow the 80/20 rule. 20% of your tweets should be about you and 80% should be about your followers. Retweeting them and sharing information you think they would like.
If you want to keep followers and gain more then you need to interact with others on Twitter. Join Tweet Chats, Twitter Parties, Giveaways, and timeline discussions. Twitter is a conversation .