Fundamental Principles for Writing an Index

What is required to write an excellent index? I mean, what does it actually take?

Indexing is governed by a lot of rules and conventions. Every indexer, including myself, tend to have their favorite strategies and style preferences. These are important for shaping and refining the index. But is that all there is?

I’ve recently challenged myself to take a big step back. While conventions and strategies are important, and I’ve discussed many here, I also sometimes feel like I am getting lost among the weeds. What is the underlying why for these conventions, and why do they work in certain situations and not others? I also sometimes notice myself and others holding onto strategies as if they are immutable rules, even when they are no longer working.

The problem is that no single strategy will work all the time. Inevitably something about the text and index will be different and will require a different solution. Being too committed to any particular approach can lead to blindspots.

So, attempting to strip away all the various ways that an index can be pieced together, what are some fundamental principles? Can a larger framework be pulled together? Is there a way to contextualize all of those rules and conventions?

This is my current attempt.

1. Every index is going to be different. This may seem self-evident, but I think there can be the misconception, especially by those less familiar with indexing, that writing an index is about following a certain template. This is indexing as a mechanical process. In the AI age, perhaps indexing as an algorithmic process. For example, this can manifest as assuming that writing an index consists of matching page numbers to keywords, and that identifying appropriate keywords always follows a certain pattern. This can also manifest as committing to a specific convention or strategy no matter what, because that is the way that an index is supposed to be or because that is what is expected. What this misconception misses is that every text, and hence every index, is going to be different. Guidelines, conventions, and preferences need to be tailored to the subject matter, the audience, client preferences, and space constraints.
2. Be attentive to the big picture. Every index is about something, in the same way that every book is about something. The index should reflect all that the book is about. The big picture also includes the larger context of how the index will be used, who will use the index, and any constraints on length or style. These factors all shape the index. Lose sight of the big picture, and the index will likely either not fully reflect the book and/or not meet the needs of its users. Instead of thinking of the index as a collection of headings and subheadings, an excellent index is more than the sum of its parts, revealing something of the essence of the book. 
3. Index at multiple levels. Details matter, from the big picture on down. Entries and arrays for the different layers of information contained within the book reflects how the book is written, provides structure, and serve the various ways that readers may search. 
4. Always refer back to the larger context. The best way to ensure relevance and clarity is to be clear about why this heading or subheading matters in the larger context of the book and index. If you, as the indexer, doesn’t know, the index user probably won’t know either.
5. Understand the tools of the trade. Indexing conventions, guidelines, strategies, and preferences are tools for shaping the index. Know the differences between tools, and when they are applicable and when they are not. Be able to explain and justify the choice of tools. If certain conventions or strategies are not working in an index, then change or adapt. 
6. Remain creative and reflective. The process of writing an index is dynamic. Circling back around to the first principle above, every index will be different. While go-to strategies and styles can be a good starting point, it is important to keep sight of the big picture and to continually adjust as needed. Writing an index is ultimately a creative endeavor, requiring careful problem-solving to create the best index for that particular text and constraints. 

I still surprise myself when an index turns out to be more difficult than I expect. There is almost always something different.

To give an example, I’ve indexed several hiking guides for a long-time client. I consider these to be easy books to index. I have a system all figured out, for the types of entries I want to pick up and how to structure and style those entries. And yet the last hiking guide I received included significantly more Indigenous place names than previous volumes. I applaud the author and publisher for making an effort to identify, include, and educate readers on local Indigenous place names, and I want to support that effort in the index. The problem was that the space available for the index remained about the same. As I realized partway through, there was no way the index, with the addition of all those new place names, was going to fit. I needed to stop, reprioritize what to include, and rethink what I choose for main entry points.

I believe if we, as indexers, can approach each index as a fresh start, assuming upfront that something about the text and index will be different and will require creative problem-solving, and be able to keep the big picture in mind throughout the indexing process, then all of the other details will sort themselves out.