I spent last weekend working on my author's platform. This includes my website, my blog, Facebook, and Twitter.
I'm relatively new to Twitter and still learning the jargon and practices of active Tweeters. My suggestion to anyone just starting with Twitter is to find a mentor. Find someone who posts interesting Tweets, someone who has a large (and legitimate following), someone who is in a field similar to yours. Follow them and mimic what they do.
I don't advise buying followers. It's seems shady and if you are trying to establish a genuine media presence, why would you want to jeopardize your authenticity and integrity for made-up followers who will ultimately not help your cause? Imaginary followers do not tweet, retweet, or like. They do not interact, they bring nothing to the table except for adding one tiny number to your following.
Consistency seems to be important as well. An active presence reminds me of your existence. In the case of Twitter, absence does not make the heart fonder. Absence makes people forget you.
Content is probably the most important feature of the entire platform. It's necessary to provide something of value to your followers. Value can come in the form of interesting information, educational info, humor, advice or feedback.
Be yourself, be real, be honest.
If you build a platform, they (followers) will come.