When I title a film, I look at the overarching theme of the film and the audience. What is the film about and who will go see it? With this combo, I brainstorm titles that I think work to impart the story and engage the targeted audience to go see it. For example, if I am titling a horror film, I will think of scary words like Haunting, Fear, Dark, Blood, Hell, Night, Nightmare, Strangers, Alone, etc.
If I am titling a romance, I will think about titles that give me the feeling of romance, such as Love, Need, You. Names of characters can work well too. If you think about it, most romantic films are based on best-selling books so they definitely have the advantage of using the book's title.
Then there are those titles that just intrigue and build curiosity about the film. Juno and Napolean Dynamite are titles that impart the feel of quirky, fun characters.
Some titles are just too long or specific. And personally, I think those are the least effective. For example, Tommy Lee Jones' film The Three Burials of Melquiades Estrada or The Assassination of Jesse James by the Coward Robert Ford are two titles that definitely don't roll off the tongue. And if they don't roll off the tongue then more than likely I'm not rolling to the theater to see them.
I like the quick, impactful title that hooks me right away, like Slumdog Millionaire, Milk, Into the Wild, Brokeback Mountain, Terms of Endearment, Good Will Hunting, Dead Poets' Society, Confessions of a Dangerous Mind, Say Anything, The Notebook, Twilight, Juno, Amityville Horror, Gangs of New York, Halloween, Dodgeball, I Love You, Man, Forgetting Sarah Marshall, 40-Year-Old Virgin, Rudy, Mission: Impossible, We Own the Night, A Beautiful Mind, Apollo 13, Jaws, E.T., Gladiator, Walk the Line, Unforgiven, Gran Torino -- the list goes on.
Titles like Men Who Stare at Goats, Hancock, Riding in Cars with Boys, Osmosis Jones, Apocalypto, Lions for Lambs, Closer, The Mexican, House Bunny, etc., don't do much for me.
I've worked on a few films that didn't even have titles as we were filming. The screenplay read "Untitled _____ Project." When I worked on Todd Solondz's Storytelling, the script was titled TS2K (Todd Solondz 2000) because there wasn't a title. I remember Animal Husbandry became Someone Like You... and I have to say that I kind of like Animal Husbandry better. It would have stood out more, you know?
So, like everything else in filmmaking, coming up with a movie title isn't easy. It takes time and a lot of thought (months, years even). But when you do figure out that perfect title, it's a great feeling, and when it resonates, I am certain it helps engage an audience and improve your chances at a successful release.