The Yoga-Sutras have a couple of nice aphorisms (from http://www.sacred-texts.com/hin/yogasutr.htm) for mind training;

"1.33. By cultivating friendliness towards happiness and compassion towards misery, gladness towards virtue and indifference towards vice, the mind becomes pure."

"2.33 When improper thoughts disturb the mind, there should be constant pondering over the opposites."