• This is the data part. You'll need to set up monitoring of your content to see when another spike is expected. If you track how fast your content is being passed along from one sharer to another, you'll know the velocity of your content. Do not mistake this metric with other velocity numbers that define the difference between the number of visitors now and an hour before. That's not predictive.
• Once you have the velocity metric, you'll have a very simple input for your promotion decisions: If this metric goes up, you can expect more people coming in the future. This is when you should start promotion. When it goes down, stop promotion and focus on other content that has higher velocity. Even if it's getting good clicks. It'll go down soon, so leave Titanic now.
• You might also want to know where to promote. I'd suggest using at least two platforms: The #1 source of your seed views and the #1 source of your viral views . For example, if your Facebook shared links are driving visitors who are then sharing your content on Reddit, you might want to advertise there as well.

That's how we do it. That's how the major "viral news sites" do it. Try it and drop us a message about your thoughts.