An appendix serves both the reader and the writer of a research paper. In the appendix, writers can include material that supports their theses but that would be distracting in the text of a given paper. Such material might include detailed descriptions of equipment, relevant mathematical proofs, research questionnaires or a detailed description of a cited author's intent. If you find yourself going off on a tangent in your paper, but you also feel that the discussion is relevant and helpful to the reader, it may belong in an appendix.
Use the title "Appendix" if you are writing only one appendix. If you are writing more than one appendix, label them "Appendix A," "Appendix B," and so forth. Center the title at the top of the page, and drop down two lines to make the first entry.
Develop separate appendices for different types of supporting materials, advises the Purdue University Online Writing Lab. For example, tables might go in one appendix; detail from another author's research in another.
Pull out relevant supporting information from the source and condense it in your own words. You may use anything that supports your paper as long as you referred to the source in your paper. You are not writing a synopsis, which would be a summary of an entire book or article, and you are not writing an abstract, which would be a synopsis with critical commentary. Adhere only to information you actually cite in your paper.
Add a short introduction and conclusion for each appendix, advises Penn State University's document "Writing Guidelines for Engineering and Science Students." The introduction should explain why certain material is in the appendix or point out possible reader confusions, given that the reader is seeing the information out of context. The conclusion might explain the significance of the data, explain the related research methodology or make another relevant remark.
Format each entry according to the citation style guide that your professor or industry expects.