“One of the best ways for freelance graphic designers and web developers to gain exposure online is with social media. Twitter is an especially successful avenue simply because it is such a common platform. Freelancers, big and small businesses, non-profit organizations, retailers, individuals – Twitter is full of world-wide activity, across every industry.”
http://vandelaydesign.com/blog/blog-promotion/best-twitter-practices-for-improving-visibility/