In my opinion one of the best ways to study for the USCIS Civics Exam is to simply watch or read the news daily.
A good amount of the exam deals with how the United States Government is made up and functions. There are news reports on these topics everyday.
A perfect example is with the proposals for immigration reform laws. The news reports that the bill must pass the House of Representatives which is comprised of 435 members, the Senate which has 100 members and then be signed into law by the President. You could learn all these steps simply by watching, reading or listening the news.
The Supreme court rules on cases at times and often journalists take the time to explain how the court works. Vacancies on the Supreme court also come up at times which forces the President to make tough decisions on whom to appoint to the Supreme court as they are lifetime appointments.
You will also hear the names of the politicians as their names come up. Names of political figures such as The President and Vice President, your state Governor, state senators or state representative could be asked in an interview.
Basically watching the news can help you prepare for you Civics interview and learn about the politics and how the government functions on an daily basis.