The title is the one of the first things a person will notice about your book. That and the cover design is what will draw people toward your book, make them pick it up off the shelf, note the author, and turn it over or open the flap to see what the story is about.
My favorite titles are ones that intrigue, like The Poisonwood Bible or The Time Traveler's Wife. If a book has a title that doesn't interest me, I don't go anywhere near it unless someone else tells me about it and gives me a reason to read. Usually I know exactly what the title of my book is but sometimes it changes and a few of my works in progress have only working titles, titles I have no intention of keeping, like Shalott.
I remember some years ago going to an all day class on writing through MPWA and the instructor told me I should change the title of my novel, Keys to the Kingdom. I insisted the title would stay. Well, smack me upside the head and call me stupid but she was dead on right. Keys to the Kingdom turned into The Way to Dendara, a much better title which also plays into the last title in the intended series.
meanwhile, I've come up with what I hope is a good one to my latest - but we'll see whether it pans out. Sometimes the first title you come up with is just fool's gold.