To write a reflection paper, you must first consider the particular audience for your piece, as well as the guidelines of the assignment. In a reflection paper, you must demonstrate personal insight into your own growth as a student, worker or person.
Reflection papers may ask students to write about their overall learning in a course. Other reflection papers may be more specifically targeted, such as those concerning teaching experience for Education courses. Some papers may be very informal, such as a journal reflection following a study-abroad experience or other voluntary endeavor.
Regardless of the particular assignment details, reflection papers should always be well-organized and stay on-topic. Avoid making general statements, such as, "I learned a lot from this experience." A better way to say that might be, "I learned how to apply my skills in computer programming to help disadvantaged students." The more specific you can be about what you have learned or improved, the more your reader will believe that you have, in fact, improved.
As with any good expository essay, be sure to included a thesis statement in your introduction which summarizes the main things you have learned or improved. End your essay with a solid conclusion which both reinforces your thesis and gives the reader a sense of the importance of your work.