Determine what ideas you want your book title to get across. Julia Child and her co-authors wanted to bring authentic French cooking to the American homemaker, who was likely to be unfamiliar with recipes or methods.
Keeping in mind the book's promise to readers, make a list of ideas of what you'd like the title to convey, and the emotional response you'd like target readers to have, and words that might suggest those ideas.
For example, if you've written a simple story to help young children start reading, your list might include:
Make the book sound appealing to reluctant readers
Let the readers identify with the characters
Reading isn't a chore
Reading can be fun
Make them want to read!