-- Search popular hashtag like Good Morning, #SocialMedia #SEO #DigitalMarketing etc.
-- Go to More Option>People and follow all tweeples.
-- Or follow from "People you may know" section.
-- They will follow you back after sometimes (wait for atleast 3 days)
-- Maintain ratio, 500 Following <> 300 Followers,, 1000 Following <> 600 Followers,, 2000 Following <> 1300 Followers..
-- After 5000 Followers your following count would be less than followers count.
-- Dont forget to followback all.
-- Use any app for unfollow unfollowers or inactive users.
-- At last check Twitter.com/RahulReply Follow there for more.
PS: I am twitter addict. :D