Everyone who twitters, either follows or blocks new users at somepoint. This is how they decide which network they want to join and whom to allow to receive their tweets. Twitter networks can be assymetric unlike other Social Networking services such as Facebook or Orkut (which are symmetric).
Other people have talked about their strategies on following/unfollowing new twitter users. Examples include Ms Bell (interesting 3Ps+S model described there). Please post in the comments section if you know of other similar posts that help you make a strategy for follow/unfollow.
Here is my way to decide upon this question:
When someone unfollows you, how do you feel?
I will feel bad. But I have not checked Qwitter for my profile yet. Okay I just did that...and...well I have to wait for them to send me an e-mail (Junk box awaits your email Qwitter).
When someone follows you, what do you do?
I make sure I check if I want them to follow me or not (bots, advertisers etc are particularly not welcome). I follow them back only if their profile is of interst to me and I think the reason for it is simply sustainability (as defined in Ms Bell post above) of my own network. I do not want too many tweets that I do not want to read (cost-benefit).
When you want to follow more people, what you do?
Mostly I find people of interest from within my network as it grows and people use new @names with interesting content in their tweets and I latch on. From time to time I use Twitnet to check the profiles of people on the edges of my network and for that matter people on the edges of other people's networks. This helps me grow my network under my control in a simple visual and more meaningful way.
When do you unfollow someone?
I only ever block people. I have unfollowed a few in the past when I find out that their views are disturbing or not appropriate. Basically my follow strategy saves me the trouble most of that time. In the past I have unfollowed and followed again as I did not have a clear strategy at that time with regard to follow/unfollow. No I have recorded it here so you can think of one for yourself too.
What happens when you have to make a decision to follow or not and you cannot?
In such cases I follow and use tweetdeck to group such people sepearately or keep them in all friends so that I can decide as time goes by. Then I can continue to follow or unfollow them later.
Your thoughts are welcome, please leave a comment below. I use twitter for Project Supervision to create a peer support group/community of interest amongst the studnets I am supervising. I also use it for my professional development. Soon I will introduce twitter in the classroom and the VLE for a true blended experience for me and my students. More on that soon. What do you use it for?