Titles can come to us in weirdest of ways, and usually when one stops stressing over them.
My novel, for example, got its title after I misheard lyrics of a song playing on the radio. A name for my character (different novel, though, and different song) came in the same way. The name of my novel's maybe possible sequel comes from a turn on a phrase from the Bible (it has nothing to do with the actual Bible, though, and I don't even own a copy myself, but the phrase fits). Accidentally stumbling across something that sparks your interest and sticks in your mind is often how the right titles are born.
Sometimes, though, you don't have the luxury of being lousy at understanding lyrics or remembering phrases from religious books you've read ages ago - then look into your own book, look for running themes, phrases, ideas, words, even characters. Try to imagine each as the title. Try to combine them. If it doesn't feel quite right, if you end up needing a reminder of how you just called your book, it's probably not the thing you're looking for.
Other times, titles will evolve from working titles. You call your novel "my werewolf novel" when you talk about it. Maybe your main title doesn't have to necessarily have "werewolf" in it, but then that functions as addition: "Moonridden: a Werewolf Novel" (the first word is courtesy of a character of mine in chapter ~10 of what I'm currently writing, but also felt fitting here).
Most importantly, make sure your title fits with what you're writing. Even one-word titles carry a certain atmosphere and rhythm to it, and you want it to match your novel's. You want to know WHY your title works for it, no matter which way you choose it.
In my WIP, the title is long and put together in an almost archaic manner, but I can afford that, because my novel deals with the past and forging old manuscripts and whatnot, and it simply fits.
Another one has the shortest and not nearly as explanatory title ("Here") - it tells of changes and clinging to what's left, both in physical and non-physical sense, and is a form of a dark fairytale set partly in a nameless world - which works for it because it raises questions and, due to its shortness, functions as a sort of spark. It throws people into the novel like a portal to another world (which happens in the novel itself), while the WIP's slowly invites them in and makes them feel like that's exactly where they belong (which again, is one of the things happening in that novel itself). I might accept changing certain words in those titles, or adding subtitles and such, but this is how I will back my choices shall it come to it.
So, if your novel is written in a somewhat analytical way, or if your narrator is keeping a diary or something, even the date title might work. It doesn't necessarily have to be directly related to the novel's main topic at all (don't forget that covers are also a tool, and can show what the title can't in a most wonderfully helpful way), but there has to be something about it that fits the style the novel's written in.
And of course, relating to my last point, always consider the rhythm. Just like you want your sentences to flow the right way, you want your title to flow the right way, and speak to the potential readers.
This turned out longer than expected. Forgive all the me-talk, but it was the easiest way to explain my points.
