By detaching yourself from the fruits of your actions and offering them up to the spirit, you learn to sublimate the ego. To achieve this, it is helpful to keep your mind focused by repeating a mantra while engaged in any activity. Karma Yoga is based on the concept of Karma. Things are seldom experienced for what they truly are, but rather for what we consider them to be. By the univeral law of karma, good actions beget good results and evil actions produce evil results.
Intention is everything.
One does not suffer for unintended evil actions, and one is rewarded for good intentions. The emphasis of Karma Yoga is not of tracking good and bad deeds, however. Karma Yoga is wisdom in work and action. The Karma yogin sees, experiences, and confronts everything with great awareness - sees it as it is, never judges. Nothing is either attractive or repulsive, it simply is.