Research begins with a question and ends with an answer. Searching is everything we do to get from question to answer. Searching success has a lot to do with the search terms you choose and the search tools you use.
Ask good questions. Look at the difference between asking "What is stroke?" (broad definition) and "What are the risk factors for stroke?" (specific, focused information). Reformulate your question to get more, precise answers. Ask "What are some of the causes and treatments for stroke?" "What kinds of therapies are available to help rehabilitate patients after stroke?" or "What research is being done on stroke?" (Stroke questions from NIHSeniorHealth: Stroke - Frequently Asked Questions - http://nihseniorhealth.gov/stroke/faq/faqlist.html#18.)
Considerdo you need to:
Find specific information? Find everything available on your subject?
Find opinions or arguments or support for a position? Find hard facts?