Karma yoga basically consists of entirely selfless service, in which the Ego is given up to the desire to serve the divine in every thing, be it man, animal, plant or an inanimate object.
Karma Yoga is also the path of doing the right thing, of following ones' personal Dharma and accepting 
destiny as it comes. If the Karma Yogi is a householder, he will accept that role as much as he would accept the role of a servant to any in need, without seeking any remuneration in the shape of wealth, satisfaction, name or fame.
Karma means action, including all acts done by the individual from birth to death. One who is not attached to his actions and performs actions because they are unavoidable, performs karma with a disinterested interest and does not adopt wrong means.
Karma performed by right means does not harm anybody and is in accordance with the law of dharma. That is karma yoga. To drop the doer from the action is karma yoga. To see oneself as a mere tool of the divine and to offer the fruit of our actions to the divine, is karma yoga. Karma Yoga is an expression of divine love, of the unity of everything that is yoga. Karma Yoga means to help, heal, and share.
Of course, solutions are as illusionary as their problems. The only help one can truly give is in promoting truth and spiritual growth, the only real end to any suffering. Thus teaching is an integral part of karma yoga and also the teacher should be aware that the result of the teaching is out of his or her hands and that the power of the teaching comes from nowhere but the divine. To teach means to let the divine word speak for itself.
We can only do four things : to act, to think, to feel and to do nothing. So if you act, act in selfless service, which is Karma Yoga. If you think, think truth, which is Jnana Yoga. If you feel, feel love, which is Bhakti Yoga. And if you want to do nothing at all, then stop everything in Samadhi, the end point of all yoga in general and of Ashtanga Yoga in particular.
---