It has been long known that prejudices begin to crack when people from different groups are obligated to work together toward a common aim. The trick is to capitalize on this knowledge and bring people together in a society where humans are free to associate with whomever they choose. One possibility is to organize opportunities for "switching places" for a day or so -- for example in workplaces where those that serve food in the cafeteria tend to come from one demographic and those that make the decisions come from another.