There are several reasons why the right keywords work at generating traffic. It all really boils down to knowing what your target audience is searching for and how they are searching for that product/service.

For example, if you are a dog trainer offering an e-newsletter that gives pet owners all the information they need to know to train their pooches, you are going to want to target to a certain audience, i.e. dog owners.

Now, just as important as providing the content...