1) What I like to do is go to a book store and look at the titles in the genre I am writing in. If you do that, you will notice that books from the same genre often have titles that are similarly structured.
For example, thrillers have short one or two word titles that relate to things hard, cold and dangerous. YA SF also has one word titles, but these words are mysterious and emotional. YA romance has humorous phrases. And so on.
So, get an idea of title conventions in your genre. These exist because they sell, so use them to create a structural frame for your title.
2) Try to write down what your novel is about in a few words. Brainstorm and don't censor yourself yet. What is the moral premise? What is the plot? What is the end? What is the character's handicap? Etc. Collect as many short phrases and words as you can.
Then try to rephrase these ideas, fitting them into the structural frame you deduced from looking at genre titles.
3) While you do that, try to imagine what your target audience wants. Why do they read? How does your book satisfy their desire. Use your intimate familiarity with your readership to further shape and finetune your title.
4) Show a selection of possible titles to your trusted beta readers, your husband/wife, your agent, your writer's group, and ask for their feedback.
5) Select a title and submit your manuscript.
6) Get rich.