Test if and how much does the headline influences and predicts the virality of a post.
Take existing blog posts and only change their headline. Track their spread and compare to the previous title. Try and find a formula that can predict virality based on these experiments.
To not influence people by the actual writing regarding the subject.
Publish only the headline. Then have people respond to it. Only then write what you wanted to write. Then people can respond to it again. Show the pre and post responses separately.