Below is Duchamp's most famous work, "Nude Descending a Staircase No. 2." As it was instrumental in the art world taking notice of him, it seemed appropriate to start here. This piece, which Duchamp created during a period in which he was influenced by Cubism, was originally censored from a Gallery (which was co-headed by his older brothers and friends). They claimed "A nude never descends the stairs--a nude reclines." 

Apparent in this work is Duchamp's mechanical style--which uses harsh lines, sharp corners, and a good deal of repetition in order to break the subject up in to it's components--and create the feeling of movement across the canvas. The piece, which follows the rule of thirds and utilizes a lot of diagonals, has almost no background, and only drab colors. The figure itself is made up of hundreds of small shapes, put together to create the image. The staircase is less detailed, and more obvious, denoting it's stationary, uninteresting presence. The painting plays with perception because it creates a kind of blurred image, reminiscent of actual motion. It is hard to make out the form unless the observer ponders the painting for awhile. But then, the mind fills in the blanks and accepts that this thing could be human.

Source: http://www.philamuseum.org/collections/permanent/51449.html