Perhaps you want to include a 'family album' of photos, cultural, ethnic, or religious information, pedigree charts, scans or photo copies of interesting documents, passenger lists, etc. Include the names of books or other materials that you used in your research. There are many books on numbering systems, find one that works for you. This is especially important for a single surname book. Other types of histories may be organized in such a way as to not need a numbering system with the exception of generational.
Genealogy is a never ending history of families and their lives.
New information is always coming to light. Remember when writing that facts are facts and can be documented. Suppositions and guesses are just that and can't be documented. A fact may turn up someday to completely change what you thought was a likely truth. A family story is just a rumor until there is proof to back it up, so be sure to make the difference clear as you write.