20% of people you follow will follow you back, as long as your profile seems compelling. Therefore, before anything make sure to optimize your profile according to the audience you want to target so people know you are worth following. When you are happy with they way you’ve set your profile, do a mass following of a targeted audience determined by a selected search criteria, after a few days make sure to unfollow everyone who has not followed you back and don’t forget about this, because you always want to have more followers than the people you follow.

ManageFlitter is a great tool to perform this hack!