Some titles come easily, and the selection of others becomes what amounts to a rampant bear.
I prefer a short title, since I love to have enough space for the artwork on the cover, and to allow the type design to stand out. This may have something to do with the fact I'm also an artist. Beauty counts, and graphic impact grabs interest, and since an eye catching cover is the first impression, it has to count. Often, now, a book cover is reduced to an icon on a website, or the small image for an audio book, and too many words create clutter.
For a complex series with different story arcs, titles that follow a pattern can help steer the reader as another, subliminal indentifier.
Simple and unique is best, because often in casual conversation people ask, and I want something that will scrawl on a napkin, not be a matter of guesswork to spell, and will be catchy enough to remember. If you have to spell it out over the phone, and it's confusing, that eliminates some choices, also. If the sales force or the book store person entering a title search into a computer is likely to stumble over mistakes or typos, I'd imagine the same thing would happen with a customer using Amazon or online ordering.
My favorite tool, latest, is the internet search - now that it's possible to keep on testing possible titles until I arrive with one that has no duplicate, that has become a fantastic help. If anyone searching that phrase finds the book first, and if nothing else using that phrase is a book, it makes finding the book by author's name less necessary, which makes less for a new reader to remember.
A few times, the publisher has changed the title I'd picked - my first nove, Sorcerer's Legacy, was once Time Splicers of Pendaire. The seventh volume of my Wars of Light and Shadow series, Traitor's Knot, was once Dark Cabal. In that case, the publisher thought nobody would know the word cabal...and the labor to find the replacement took months. I was saved, that time, by one of my test readers, thank goodness, because I'd tried everything over the hair-tearing course of several months, and come up utterly dry.
When I pick out a title, often I will take a sheet of paper and write every descriptive word and every identifying noun that could be a tag for the plot. Then I mix and match, and spring board off them, putting them through various grammatical forms. Often, by the second sheet of paper, I have a list of five that will work. The elimination round is the google search. Then I send the winning one to my editor and hold my breath until it's accepted.
If not, back to the scratch pad. Again.
Causes Janny Wurts Supports
FINCA Heifer International American Indian College Fund Trust for Public Land Doctors Without Borders Environmental Defense