What you want to do is shade in or colour all the parts of the drawing that aren't being hit by light. So as you can see in the Spider-man picture, the tips of his head and shoulder are being hit by light, but the chest area is almost fully coloured with barely any white spaces. So you can choose a light direction or just copy the one above (which is the light is coming from behind). When you're shading/colouring just go crazy, but make sure you leave spaces for when the light hits the object that you're drawing. To get the same sketchy effect just try to free up your hand a bit, maybe change the way you hold your pencil, what this does is also makes the lines you draw less rigid and precise.
Unfortunately I don't know the name of the artist but I found got this image from Imgur, posted by a user who goes by the name of "Wingevil". He has posted more cool related things so feel free to check out his page. Wingevil Submitted Gallary