When you are indexing a document, that is, creating an Index for a document, make sure you observe the following three golden rules for maximum user satisfaction:
1) Limit your Index to a maximum of THREE indented levels. Human mind starts losing track of the nestled groupings once you cross over into the fourth level and beyond. It helps a great deal if every level has its own styling. For example, the first level could be in BOLD letters, the second level in normal PLAIN fonts, and the third in plain ITALIC fonts. I’d recommend to use the same font family and not switch to different fonts in between indentation levels.
2) Always start your indexed words with LOWER CASE letters, unless it is an acronym. Lower case letters is easier for the human eye to read. But all acronyms should be in all caps. It is great practice to repeat every acronym also in its open form, starting each word with UPPER CASE letter. For example, repeat “ACS 115” also as “American Cancer Society 115”, but not as “american cancer society 115”, etc.
3) Make sure all important phrases are CROSS INDEXED, cross referenced, under their respective letters. For example, repeat “space shuttle” also as “shuttle, space.” In this case both are under the letter S. Repeat “welfare state” as “state, welfare” under the letters W and S, respectively. Do the extra work if you want your users find what they are looking for easily. Cross-referenced index entries will prevent the users from thinking. And a user that can go through a document, book or manual without thinking is a happy user.