How to identify a research question

This year is my second year of doctoral study.After passing the exam, the most important thing is to identify my research interest. On my way to Downtown campus, I talked to one of my classmate about how to find a meaningful research question. Basically, he summarized two ways-literature-based and problem-oriented methodology.
Tonight's class is an fascinating one with a focus on research design. We talked about big issues existing in our field. He argues that contemporary American public administration does have its big issues or concerns. That is, what can governments do? How can it do efficiently? Governed by this big concern, the question can be divided into four subareas: first, how well can public interest be protected by private interests? Is current reform good to make government to meet the 4E criteria (Economy, Efficiency, Effectiveness, and Equity)? Is privitization helpful? Second, the ethics in public service is another crucial issue. What is the foundation for public administration? Democracy? What are the sources of ethics? Third, Organization studies. How to manage efficiency in organizations? The forth one is about the social trust. How do we build social trust? Why is public trust lower than it used to be?
We also spent lots of time discussing about the origin of modern government. It originated from Locke's thought. According to him, Locke used scientific methology to develop his arguments as well. First Locke came up with the hypothesis that EveryOne is born equal. This is a hypothesis because it is not true in reality. Then, Locke moves to argue that each person has the right to achieve happiness. To protect the security, finally people reach an consensus to build a government to protect their right. And, Jefferson ideas came from Locke apparently. In sum, the origin of modern government derives from Locke in that he establish the modern government's criteria, and the purpose of government. Then, the next question would be how to build government? Public administration, according to John Mill, is to produce efficiency to sustain demorcratic goals. This is also why Wilson brought up the popular principles to implement policies.
The last topic discussed tonight is about the philosophy of science. Scientific Approaches refer to a systematic ways to conduct research--an empirical emphasis, emphasis on facts and a strict way to collect facts,pose hypotheses and verify and so on. Scientific approach differs from positivist approach, which is a sprit of science....Except positivist approach, interpretivist approach can be scientific as well unless it goes to another extreme.