Only this: watch it, educate yourself, and remember that evil is not a supernatural force, it is human.
12 Years a Slave
Chiwetel Ejiofor stars as Solomon Northup, the New York State citizen who was kidnapped and made to work on a plantation in New Orleans in the 1800s. Steve McQueen (Hunger) directs from a script he co-wrote with John Ridley, based in part by Northup's memoir. Michael Fassbender, Brad Pitt, Benedict Cumberbatch, Sarah Paulson, and Paul Giamatti co-star.
12 Years a Slave is a beautifully shot, unflinching, and unrestrained portrayal of slavery.