Read through the entire book. While you are reading, pay attention to main ideas and concepts that would interest a researcher. If you are creating an index for someone else's book, ask the author to help you determine the important concepts and ideas. Each time you find main ideas, terms and concepts that you initially think are important, jot down the page number on which the information appears.
Go through the list of concepts and main ideas to start making a list of terms that will appear in the index. This list needs to be complete.
Make sure that every reference of each term is listed in the index. One of the best ways to do this is to search for each term using a word-processing program. Type the desired term in the search window and press the "Enter" key. This will pull up every mention of the word you want. Again, note the page number of each reference, as this is what will make up your index. Your list should include words, terms, people and concepts, with a list of page numbers next to each entry.
Put each term into alphabetical order. Basically, this is where you type out the index that will be in the final book. Double-check that the order is alphabetical, and then double-check that each page is correctly noted.
Make sure all spelling is correct. The book is most likely being checked by a proofreader while you are creating the index, so you do not want to slow progress to final publishing by having the index stuck in proofing.
Find a friend to double-check your work. If you have not done many indices, it can be helpful to find a friend who is detail oriented to look over all of your work.