The over/under method is one of the best skills you can learn on a set — especially if you can do it fast.
ALL cables - mic cables, light cords and extension cords should be wrapped this way every time!
Winding a cable over your arm is a sure way to ruin an expensive cable. It causes the cored to have spirals in it when it is laid out and damages the braided wires on the inside of the cable. Using the over-under method will help the cables lay flat and last forever. I've got 40-year old cables at home that work as well as they did when they were new. I've seen brand new cables ruined in a matter of months because the were wound the wrong way.
The method is best taught in-person, but the following references may also be helpful.
Short, sweet and to the point.
https://www.youtube.com/watch?v=-74OEVUOKOw
Not too long and includes some good background on why it is important.
https://www.youtube.com/watch?v=x-sO62Gvqp4
This one is pretty long and in your face. The guy in the video is a lefty and he's not very fast.
https://www.youtube.com/watch?v=MziOBf60Kn0
We used a piece of TV coax, which is one of the nastier examples for stiffness and general misbehavior. We figured that if you can successfully flip-coil this stuff, you can handle anything else -- even heavy stage-pin cables and sound snakes.
Hold one end of the cable in your receiving hand, and grab another part about 2 feet away farther down the cable.
Make the first coil normally by bringing your hands straight together, and accumulate that coil in your holding hand. Rotating both wrists slightly counterclockwise will help the cable bend the right direction. Let the cable spin in your hands to form a nice round first loop.
Grab another piece 2 feet away, but as you bring this one in rotate your wrist clockwise to invert the loop as it forms. It often helps to also roll the cable slightly between your thumb and fingers, to better guide it into flopping the right way. If the loop starts to twist funny or try to figure-8 on you as it forms, twisting the cable in your fingers helps to flatten out the loop.
Add this inverted loop to your bundle. The part that heads for the floor should pass UNDER the loop you're just making -- this is the key ...
Now repeat the process normal - under - normal - under until the cable is wound.
Secure the cable with a velcro tie or for big cables use a string.
Certification
Demonstrate that you can properly wind a cable.
Practice until you can do it without thinking about it.