After going to the trouble of adding people to your social network, you don't want to lose them. Keeping people in your social network is as difficult as getting them in the first place. So, what's the secret?
First of all, develop personal relationships. When your posts start to feel like advertising or spam, you can count on losing friends. Participate in conversations. But don't be so eager to assert your opinion that you come off as a know-it-all. Give-and-take conversation is the foundation of social networking.
Many people will send you a "getting to know you" post when they add or follow you. If the response is automatically generated, it's okay to ignore it. But if someone takes the time to send a personalized message, you should probably take the time to respond personally. If the other person doesn't receive a personal response, he or she may drop you from their list.
Of course, you don't have to wait for someone to approach you. When you notice someone new following you or someone adds a comment to your wall, take the time to send them a personal message. Auto replies are worse than no reply at all. Instead, invest a few minutes in writing a genuine thank you to the person following you.
Replies and @conversations on Twitter are what people want in the world of social networking. Look at your posts. If they're a series of statements about what you're doing, reposts of news, research studies or announcements that you have a new blog post, you can't expect to hold onto readers for long. Read the posts of the people you're following. Respond when you have something helpful, witty or relevant to say. Look for opportunities to add something of value to the community.