Welcome to care2 community. This article will show you how to gain more twitter followers in very short period of time. So let's start.
1. Rule and most important of all. You need to post interesting tweets, you want your tweets to be re-tweeted as much as possible. It's free promotion to your profile.
2. Follow other people and engage with them. Comment their tweets and make sure you are kind to them. They will most likely press follow back.
3. Have a website or blog? Great. Post your twitter feed into sidebar and add follow button.
More interesting tips for twitter can be found here: 6 Tips to gain more twitter followers