Karma Yoga is selfless service to others, selfless meaning not expecting anything in return. Examples are working for charity, working for kids&youth clubs, working for whatever cause that helps others.
For me, changing the world begins in myself, tuning myself to others and the world. I am especially sensitive to health, nutrition, education, environment, children and youngsters. These are what make the future of this world.
Therefore, my Karma Yoga usually consists of one or several above-mentioned topics.