There are many ways to gain background information about policies. You may need to search in more then one place to get a complete picture of the sitation. Some places to begin your search:
Social historians and other scholars often publish books about particular social issues that cover the history of a social problem, causes and responses, and give an overview of the relevant policy making. Use the links in the Subject Search for Books to start your topic search
Once you have identified a particular policy or piece of legislation, the Wikipedia page for it may have convenient links out to relevant government documents and research reports. Use those links to find resources.
Example- A search for Amber Alert, we learn that The United States House of Representatives adopted H.Res. 605. We can use this information to search for the piece of legislation now that we know the legal name.
Depending on the social issue you choose to analyze; there are many other possible resources you could search. For example: if your choice is education-related you may want to search in the database ERIC.
The Future of Social Work: What next for social policy? by