To find topics of interest and discussions around them, use Twellow and Mailana

1. Run a search in Twellow using the words “ ______” you want to follow
2. Run a Twitter username in Mailana.
3. Discover the people network around the subject.
4. Choose some of the people to follow.
5. Use Search Twitter to follow conversations.

Twellow click here
Mailana click here

Source: Thanks to Marshall Kirkpatrick