Taken from https://www.portlandwritersmill.org/07/the-joys-of-title-research/

Title research is not essential, but if you want people to find and purchase your book, your first task is to get them the book in front of them. All bookstores, and especially Amazon, are like huge haystacks with your book like a tiny needle hiding inside. But if your needle appears when they look for that bright red rolling pin, your book is more likely to be found – especially if it’s a book about cookery. If your need appears next to the machinegun and it’s a book about cookery, well… less effective in generating sales perhaps…

1. First think of some titles
2. Look at what ties them together. Did you find
   yourself using the same word or phrase in lots of title options? They become
   your key phrases, and now you want to test if they’ll help sell your book.
3. Start with Google and keep in mind, this only
   works once per machine (unless you’re making sure to search anonymously in a
   private browser) – Google gives you the answers it thinks you want, so after
   one search it refines its idea of what you want to see.
   1. Begin typing your “key phrase” and watch for the
      “completions” that Google offers (i.e. type slowly and keep your eyes open!) Are
      they appropriate to your topic, or is someone looking for your topic going to
      turn away in horror and look elsewhere?
   2. See what appears on the Google search page too.
      At the top are the things people have paid to have appear with that “key
      phrase.” Are they related to your topic?
   3. Lower down the page are all the other things
      Google thinks you’re looking for. How well do they fit your theme?
   4. Look for famous authors, books that might be
      vaguely similar to yours, topics that might be related to what you’re covering.
      And reject the key phrase if everything that comes up appalls you.
4. Now try an Amazon search. This time it’s not as
   geared to you, so you can repeat it. Start typing your key phrase, see what phrases
   are offered as completions, and look at what appears on the page.
   1. Remember, with Amazon you might type in “This
      book by this author” and find the book itself doesn’t appear until the third
      page of the search. Google tried to give you what you wanted. Amazon tries to
      give you what will sell.
   2. What you’re looking for is whether any books appear
      such that the people looking for them might be tempted to buy your book.
   3. You’re trying to put your cookery book next to
      the bright red rolling pin in the haystack.
5. Finally get someone else to do the same searches
   with a couple of “final options” for titles, and see what they find.
6. Remember, titles are not copyrighted. It doesn’t
   matter if you share a title with someone else.
7. Remember too that you can have a subtitle. If
   there are “key words” that you really want to include that don’t fit the title,
   put them in the (long) subtitle. Some researchers claim really long subtitles
   help sell books.