I've been asked how a writer gains followers on twitter and I'm happy to share what I have learned so far, along with a number of useful links. 

Your posts should not be a stream of self promotion; to receive you must first give. I endeavour to post one twitter story every day, through which I maintain a presence and offer something to the readers.  Don't post too much to Twitter at once; there have been spirited discussions about how much is too much with many suggesting the line be drawn at six posts per day.There is no definitive answer but I rarely post more than twice a day.
 
Using hash tags to categorize your tweets will be helpful in increasing your following since it puts you in front of people who may not already be following you. When posing twitter stories I use the #vss tag. Other useful twitter tags for writers can be found at
http://nicolehumphrey.net/2010/05/25-favorite-twitter-hash-tags-for-writers-clickable-list/

It is good manners to  thank everybody who follows you or mentions you in their tweets. Retweeting the stories of others will get you some attention from like minded people.

There are a number of publishers of twitter fiction. Having your work accepted and showcased by these may increase interest in your personal posts. A downloadable .pdf file is available on the Twitter Fiction page of my website with twelve publishing opportunities for Twitter fiction writers. http://www.ficklefiction.com/twitterfiction.php.

At www.leilimckinley.com,  have made a free ebook available for downlaod, '65 Ways To Use Social Media to Sell Your Book', Leila also runs a number of courses on different aspects of social media as a marketing tool.

Maintaining other social media, such as Facebook can increase your web presence. Twitter and Facebook can be connected so tweets automatically appear on Facebook.  I learnt how to do this from instructions at the link below. There are many other interesting how to's on this site.
http://michaelhyatt.com/how-to-update-your-facebook-status-with-twitter.html

"Tweetdeck" http://www.tweetdeck.com/ can be used to simultaneously post tweets to Twitter, Facebook, Linkedin, Myspace, Buzz and Foursquare. 

Above all be courteous, respectful and don't spam. Offer something of interest to others and be patient, it takes time and consistent work to build up a following.

Thanks to all those whose links I have included in this post and from whom I have learnt so much.
 
Best regards

Gayle www.ficklefiction.com