Karma yoga is the union with God by doing. We can say it is "Yoga of Action". But what actions and how they need to be performed. In this context, the principle of Karma Yoga described in the Gita is most acceptable. Bhagavad Gita says that doing nishkama karma, the karma with non attachment, non desire, non intention is the way to attain yoga. What Lord Krishna says more on this, lets see.
Dharana - The concentration. Maharishi patanjali has compiled the yoga sutra on Dharana as "Desha Bhandhashchittasya Dharana". Focussing the chattering mind is necessary whether it is day today life or spiritual life. No work can be accomplished without focus. So lets understand the sutra for better lifestyle.