Never include an appendix that isn’t referred to in the text. All appendices should be summarized in your paper where it is relevant to the content. Appendices should also be arranged sequentially by the order they were first referenced in the text [i.e., Appendix 1 should not refer to text on page eight of your paper and Appendix 2 relate to text on page six].
There are very few rules regarding what type of material can be included in an appendix, but here are some common examples:
Correspondence -- if your research included collaborations with others or outreach to others, then correspondence in the form of letters, memorandums, or copies of emails from those you interacted with could be included.
Interview Transcripts -- in qualitative research, interviewing respondents is often used to gather information. The full transcript from an interview is important so the reader can read the entire dialog between researcher and respondent. The interview protocol [list of questions] should also be included.
Non-textual elements -- as noted above, if there are a lot of non-textual items, such as, figures, tables, maps, charts, photographs, drawings, or graphs, think about highlighting examples in the text of the paper but include the remainder in an appendix.
Questionnaires or surveys -- this is a common form of data gathering. Always include the survey instrument or questionnaires in an appendix so the reader understands not only the questions asked but the sequence in which they were asked. Include all variations of the instruments as well if different items were sent to different groups [e.g., those given to teachers and those given to administrators].
Raw statistical data – this can include any numerical data that is too lengthy to include in charts or tables in its entirety within the text. This is important because the entire source of data should be included even if you are referring to only certain parts of a chart or table in the text of your paper.