A) It's "X" shape
Most birds have feet with three toes forward and one toe backward. Roadrunner feet are zygodactyl, which means two toes point forward and two point backward--you can see an example of this in the image below. It leaves unique and easy to identify, "X"-shaped tracks approximately 3" long and 10" apart.
Photo: http://www.wandrin.us/Wandrin2005/RoadRunner-26.jpg