Here is a great FAQ page by the UK Society of Indexers.
Is it indexes or indices?
An exhaustive explanation by the Grammarist. Indexers generally use “indexes” for the plural.
Why should I hire a pro?
Norms: Professionals are up-to-date on the latest rules for indexes. There are many rules governing indexes, and they do change. Publishers often have preferences, and professional indexers have been trained to follow them.
Software: Specialized indexing software is expensive, and not something one would buy for a single job. It is also very powerful, but does take time to learn.
Speed: The index is usually written just at the point that the book is ready to go to press. A delay in the index can play havoc with the publisher’s schedule. It’s no time to be learning complicated new software.
What kinds of books do you index?
Cookbooks are my specialty. I am a former professional cook, and have a library of over 400 cookbooks. So it’s a natural fit.
I also index trade books (books for the general public) on most other topics.
What are your rates?
Rates depend on the complexity of the material, the deadline urgency and the style/size limitations of the index. Please contact me to discuss your needs.
Oh no! I’ve already published a book and now I realize the index is awful! Now what?
All is not lost. Many first-time authors aren’t aware how important an index is to their sales. I’ve got a solution that will actually solve this problem for your already-published book, and lead to MORE sales of your future books. Contact me to find out how!
Cookbook Indexes – what’s so special about them?
Cookbooks are so special that I’ve devoted a whole page to them!