Choose an industry, based on interest in the industry. Examples of industries range from advertising to zoos, and include digital watches, private jets, diapers, over-the-counter cold and flu formulas, photographic film, automobiles, airlines, football, romance novels, dating services, banana production, or pre-stressed concrete, computer printers, pagers, business schools, used cars sold over the web, movie theatres.
Having chosen the industry, you will need a question or issue on which to focus. Such questions could be broad (What strategies are most likely to sustain profitability?) or narrow (Should firm X build a new plant? Where?). Good questions encourage you to think strategically, and thus should include the likely responses of rival firms to any hypothetical actions. Plan to include your question in the topic proposal. A different approach is to choose a story about the behavior of a firm from a newspaper or other source, and research this story. For example, the defense contractor Lockheed-Martin announced a friendly takeover of Northrop-Grumman, and then later dropped the plan after the Department of Justice filed an antitrust complaint. This story contains a dozen potential paper topics. How is the defense industry organized? Why did they want to merge? Why did the DOJ want to block the merger? Choose a topic in which you are interested rather than one that looks easy. Topics that look easy can be treacherous and unpleasant if they are boring.