I usually base it on the movie's stars, theme or genre, then read up its synopsis (short movie description on imdb or theater's website), and if it's less likel

I usually base it on the movie's stars, theme or genre, then read up its synopsis (short movie description on imdb or theater's website), and if it's less likely to have some kind of twist or I don't mind spoilers at the time, then I'll watch the trailer. I'm also not really picky, so don't mind giving a movie a try without knowing anything about it in advance (Dancer In The Dark, Oldboy, and Snowpiercer come to mind as wonderful surprises, for example).