There are many types of policies that originate from many sources. In this chapter, we review these and how they have been developed over time. We illustrate how many policies initially targeted at-risk or problematic groups and how more recent approaches have shifted toward thinking about entire populations. All such approaches include strengths and weaknesses, which often relate to the lack of a clear evidence base prior to implementation. Scientific evidence is increasingly regarded as a helpful addition to many theories of behavioral interventions, hence the increased use of evidence-based policy frameworks. As theory has to be balanced with pragmatics to be useful in policy, a practical pathway model for the development of evidence for policy evaluation is introduced.