Pick a social topic you want to study. Think of your interests or what is relevant in your culture to help you pick a topic.
Find a sociological theory that helps to explain the topic you chose. It helps to break your topic down to its basic issue. For example, the separate 2011 protests in Egypt, Libya and unions in the United States could all be explained using social movement theory, since they all break down to the common issue of social movements.
Use your theory to explain the topic you chose. The paper should both explain the theory and how it could be applied, using your specific case. Write how your topic is an example of your theory and how your theory explains your topic. If the theory does not completely explain your topic, include that in your paper. Theories are not all-encompassing.
Introduce your topic in the first section of the paper. Since it is a reflection paper, you can write the facts of the topic as well as your perception of it.
Explain the theory you chose in depth as if you are teaching it to someone who has never heard of it. This is the second main section of the paper. It should not include the sociological topic, but only focus on the theory.
Use the theory to explain and analyze your sociological topic in the third section of the paper. You want to show why that topic occurred, using the theory to explain.