1) Try to re-tweet as much as possible and encourage other peoples to re-tweet. Tweet on your favorite subject in which you have deep knowledge. This way people will know about you and your ability in the subject and lot of people from same interest will follow you.
2) Your twitter page should reflect your identity. Give brief details about you and your profession on twitter page. It would be good if you could design twitter page in a way that reflect your identity. for example, if you are singer you can use music related picture in background. To achieve this you can hire professional service.
3) Follow other peoples from same fields and interest. It is possible some people will follow you and some will not but it is necessary to increase your followers count. As much as you will be active on this more you will get in return.
4) Stay active on twitter atleast half an hour. Read other people tweets and give your comment on tweets if you like to do. This way other people followers will see you and more likely they will follow you.
5) Try to re-tweet as much as possible. Keep in mind, more re-tweet more followers. Always try to tweet on subject that have wide public interest. On public interest subject you will get lot of comments.
6) Stay active on twitter continusely otherwise you will be out of main stream. Get a trusted tweeter professional help if could not get time to tweet.
7) Follow popular peoples and read their tweets regularly. Keep eyes on their tweet style. You will learn lot from other peoples tweet.