I call it the WW-H Method.
Here's the principles behind the method:
1) do not give all the information in the actual article
2) the resource box should be about the reader and not the writer
3) give a benefit in the resource box to get the click or email
Here's the method:
1) Find a problem that people want to solve.
2) In the article tell what (W) they have to do to solve the problem. This builds credibility for you as you show you have knowledge.
3) Also explain in the article why (W) they have to do what you have told them to and the benefits they'll get by doing it. This further builds credibility, but also builds desire to actually do it to get the benefits.
4) In the resource box offer to give them the how (H) to do it. Make the resource box flow from the article and appear to be like the final paragraph. along the lines of:
So there it is - do ABC and get DEF benefits. If you would like (to learn the quickest way of doing this / a tool that will do it for you / use a service that will do it for you), then visit XYZ site.
In summary, give the what to do and why in the article to create desire and credibility and offer the how to do it in the resource box.