Ordinarily, professionally, I am not indexing for myself. I am indexing for anyone who might pick up a copy of the book.
Indexing is both an art and a service. You have to imagine yourself into the minds of others and build an index that speaks to them.
Different people have different vocabularies, and different reasons for approaching the same book. Even a cookbook might be read by a professional chef, an experienced home cook, and someone who has never scrambled an egg. It might be the first time they’ve opened the book, or they might be trying to find that minced lamb recipe they made a while back, the one with crepes and some kind of spicy tomato sauce.
I was motivated to index A Writer’s Diary for personal reasons. I want it to serve me, which means I may pick up little idiosyncratic things I know I’ll want to find later. But I also want to create an index that will serve the needs of other writers. That means I must think about what they might look for, and how they might describe it. And the old reference librarian in me keeps nudging, saying well, what about the scholars? What about the biographers? Who else?
I am unusually free to do this here! In the average professional project, there are space limits. Indexes often get whatever pages are left over at the end of a book. You can try to negotiate a smaller font, more columns, but you rarely get free rein to index everything you think is worth indexing because it costs money to add another signature for the sake of an extra page or three of index. So you have to make choices. And then you have to stick to them. If you’re picking up a topic, pick it up every time. If you’re not picking it up, you must pass it by, every time.