First cut the skin from the top and tail of the orange, then sit one cut side on the chopping board. Working from top to base, slice the peel and pith away from the flesh in strips. Try to take away as much pith as possible, but if there is any left cut it away with a small knife.
You will now be able to see the contours of each orange segment. Cut along the edge of each segment, leaving behind the membrane, to free it from the fruit.