The image shows one door in two sides of entering and exiting. If the job is done well, it should be easy to tell which one to push and which one to pull
Push the left one and pull the right one :]
I wanted to give it a go designing 'user-friendly' yet aesthetic doors.
The rectangles are positioned in a triangular shape to helps direct the user towards the side they need to use (towards the handles) . Also, on the side one is supposed to pull, the rectangle protrudes slightly.
A rather great book helping me to get my head around it is The Design of Everyday Things (author worked as an adviser for early Apple) . It analyses both poor and great designs of everyday objects focusing on user experience .
It has been a mind-opener for me, with a kind of key message: when having trouble using a product/object (be it phone, DVD player, doors etc.) users tend to blame their clumsiness when in fact it's the fault of design. On the other hand if the use is effortless and intuitive, doesn't require explanation it is yet again because of the design!