Effective research starts with the selection of a good topic. A good topic has three characteristics:
Once you have a topic, see if you can put together a sentence that explains what you are researching and for what purpose: "I am researching ____________ in order to ____________."
For example: I am researching the government's exercise of the right of eminent domain in light of the most recent Supreme Court decisions related to this subject in order to assess the degree it impinges on property rights.
Now, take your statement and transform it into a thesis statement (i.e., the proposition you are arguing):
Recent Supreme Court decisions on eminent domain have significantly impinged on individual property rights.