How to render the black lines at the edges of an object? How to render an image like this with black lines ? 



Image taken from the following faceboock page: https://www.facebook.com/glenyrenner/posts/1308258389303606?pnref=story
It is called Freestyle Line style

Add a base color and in the Render -> Freestyle (tick mark)



If you want to change the color of the stroke (line)
Under Render Layer -> Freestyle Line style -> color -> Base color (change the color from black to any color)



Hit F12 to render after finishing the render wait a second to complete the Freestyle Line style render and you can see a outline of the color.