Background reading helps you to better define and focus your topic (e.g. immigration policy in the U.S. or China? Current polices or how a policy has changed over time?). When you do background reading, you also try to get a sense of all sides of a particular issue. You better understand key figures and key events that pertain to your topic. Another important aspect of background reading is to make you familiar with key terms that will become important as you develop your search strategy.
Try not to rush through your background reading, and be prepared to return to it at various points in your research. A solid understanding of your topic (and broadening or narrowing your focus, as needed) will probably save you time in the long run.
OneSearch is a great place to find reference sources quickly and easily. It's that big search box that you see in the middle of the libary's website. When you get your results, filter by Source Types and then select Reference Resources (filters are on the right-hand side)
We also recommend:
Opposing Viewpoints. Helps readers get background on both sides of important political issues and current events
CQ Researcher, which provides in-depth reporting on current political topics
News articles are also helpful as background sources. Try the library's News and Newspapers databases in order to see how multiple reporters cover a given story.
Read critically when you use Think Tank Search -- or any think tank sources. Consider New York Times reporting, How Think Tanks Amplify Corporate America's Influence (August 2016).