With my fourth novel I am currently working on, like The Beach House, the title came to me before I began writing. I won't reveal it just yet, but suffice to say it has a lot to do with the theme of the book once again.
If you are struggling to come up with a title, just let it be while you write. Don't stress about it or try to force it - you will come up with something eventually. Think about the books you have read and how their title relates to the stories within. Try and come up with a short list or even just have a brainstorming piece of paper handy where you can write ideas. Do check out Amazon and see how many other books there are by the same title, of course there is no copyright on a book title, but if there are dozens by the same name you don't want to get lost in the middle of a huge list. It can be hard to let go of a name you may have picked back in your childhood for your first book, but you have to be practical too.