First and foremost, overnight salting is the most important step for prime rib. Others may try to fool you into thinking it's the resting stage, which is up there for sure, but it's not number 1.
Rub a good quality kosher salt all over the meat the day before you want to cook it. Now, place it in the refrigerator overnight, UNCOVERED in order to enhance the beefy flavor while dissolving some of the proteins, which yields a buttery-tender, juicy roast.