Avoid vague questions that could lead students to different interpretations. If you use the word "how" or "why" in an essay question, students will be better able to develop a clear thesis. As examples of essay and short-answer questions:
Poor: What are three types of market organization? In what ways are they different from one another?
Better: Define oligopoly. How does oligopoly differ from both perfect competition and monopoly in terms of number of firms, control over price, conditions of entry, cost structure, and long-term profitability?
Poor: Name the principles that determined postwar American foreign policy.
Better: Describe three principles on which American foreign policy was based between 1945 and 1960; illustrate each of the principles with two actions of the executive branch of government.