Begin with a comprehensive literature search of past and present information about your subject-- you need to know your subject thoroughly.
Be specific in your focus: If your focus is too broad at this point, you won't be able to control all the factors that may affect your study.
Collect your observations from the literature, and from this information begin asking specific questions. Research again, looking for the answers to your questions. Use the unanswered questions to form the basis of your research question.
State your research question in a form that can be tested and analyzed -- this is your hypothesis. Specifically state an intervention and a predicted outcome, often in an "If...then" statement format. Analyzed the results at the end of your study to either support or falsify your hypothesis.