Slowly. Painfully. Patiently. Most of the time, badly. :'D
In general, I'm trying to look for something relevant to the story itself, a word or phrase that sums it up or shows the core theme behind it. Whether it's the title of the whole thing or particular parts, I'd like my readers to get an idea what it'll be about... Or even better, I want them to think 'oh, now I understand where the title came from' when they finish
To be honest, I'm not quite sure if it even makes good titles. I feel many of them are not catchy enough to attract the reader's attention. I like it when they stay true to the story, though, even if it comes at the cost of some publicity. I know many people would disagree, and for perfectly valid reasons